Some practical thoughts from Susanna:
Don't put any preparations off! I cannot stress this strongly enough! Start now and feel urgent about it! Do the most physical tasks first and work your way down to the least physical. For instance, go from making freezer meals & shopping, to sewing, to setting up and organizing baby supplies - and save planning/writing activities for later on - lists, schedules, etc.
Freezer meals! What worked very well for me was to plan one or two "sessions" a week. I would make 3X a recipe, freeze two and serve one for supper that night. We can get disposable aluminum 9x13 pans at the Dollar Tree two for a dollar. Label each casserole or bucket of soup with its contents and simple clear instructions for preparation so you aren't necessary for that part later on. Keep a list on the fridge with what meals you made on each date so that you can eat them somewhat in order. This works better than dating the meals themselves. Post-partum, save those meals for when you aren't getting any more from others & try to stretch them out as long as you can, saving them for extra-busy days. Ours lasted until the babies were almost five months old, and I was able to get the summer sewing (easy one-hour T-shirt dresses) done for the girls before the meals ran out. You will be SO thankful for EVERY meal you freeze! I encouraged myself with this thought while making all those meals in the summer heat! By the way, this plan worked so well that I still plan a freezer meal session every three or four weeks, but now we have more and bigger eaters, so I make 4X a recipe and put three away! This method fit well into normal life and wasn't overwhelming until I couldn't physically manage it anymore and Dh told me to stop.
Baby supplies: Only use cloth diapers if someone other than you is completely in charge of laundering them. This holds true until the twins are sleeping through the night at the minimum. Also, don't skimp on baby supplies. It will save you valuable TIME to have very big stacks of burp cloths, onesies, stretch suits, receiving blankets, sheets and waterproof pads - anything that you use often and gets dirtied fast. The waterproof pads are great to put in the bassinettes under their bottoms, so if their diapers leak, it is contained, and you don't have to change the sheet, too. I'd never bothered with them before the twins. My babies spit up a lot the first few months, and if they spit up on one end of their sheet, I'd just lay them the other way until that side was dirtied, too. I hope you are as blessed with lots of good thrift stores in your area as we are in ours! We didn't lack any supplies we needed when the real test came. I did, however, have too many socks - they don't get dirty fast! Borrow what you can - clothing, bassinette, sheets - especially what you only need shorter term.
Try to set everything up that you will need for their care in as compact a place as you can, to save steps. You will get to the point where you are grateful for even 5 minutes saved so you can lie down that much sooner. We put everything in our bedroom: Along one wall was the changing table (we found for $12 at a yard sale and which we're still using) with a large diaper stacker (given to me) hanging at the left end and a pocket organizer (found for $1 at a thrift store) hanging on the right end. To the immediate right was a wheeled four tier metal cart with wipes, etc. on the top. To the right of the cart sat our Dekor diaper disposal system - like a Diaper Genie, but with greater capacity. (My husband put his foot down about cloth diapers and said that we would economize somewhere else!) Along another wall we set up a loveseat (30% off at a thrift store) for nursing the babies. It is soft and comfy and has a back high enough for me to lean my head against and thick enough for me to stack burp cloths on! I needed a long-term, comfortable solution to the HOURS and HOURS I would spend sitting and nursing them - tandem, of course, to save time and stimulate better milk production. This tandem nursing is impossible to do discreetly, so our rule was: only girls allowed in; boys had to talk to me through the bedroom door! (We got used to it!) I put a small pillow in the middle of the loveseat for back support and a bed pillow along each arm. To nurse them, I would lay them side by side on our bed, strap on the twin Boppy pillow (indispensible to me - It is wider all around than a regular Boppy and has wide velcro straps in the back. I found it at a twin yard sale for $3), adjust my shirt for nursing, scoop up the left hand baby, then the right hand one, back up like a Mack truck (beep, beep, beep) and sink gratefully into the loveseat with my feet propped on a nursing stool (given to me.) The bed pillows supported the sides of the Boppy. After getting them started nursing if necessary, I was hands-free. I didn't start this until they were both nursing at 6 1/2 weeks. Probably I would not have been hands-free for the first weeks, I'm guessing? I had a floor lamp and small stand to my right, and my Dear Husband found a small hospital-style bed table that sat to my front right as I sat there. I could write thank you notes (stock up on these now!), letters and other things, reach the phone (but because the door was closed, I only used this if I had to, as the older boys often needed to talk with me), my BIG water cup, healthy snacks, books to read tissues, lanolin (I did get sore, but not for long and the lanolin helped), etc. etc.
I don't think I would have been able to nurse them so thoroughly (I didn't start solids until they were about 7 months) and so long-term (until they were 14 1/2 months and I weaned them for the sake of this next one) if I hadn't had such a workable situation set up. For it to be sustainable, I had to be able to multi-task, I had to be comfortable (I tend toward back trouble), and I had to have privacy.
Scheduling - Along with training the children in more food prep tasks, they should be trained to do the laundry if they aren't already. Other skills to teach: changing sheets, ironing, outside work, care of the younger ones. Try not to do anything that the children could be doing - stick to what only you can do. Even if you get outside help, you will need to depend on your children to keep the basics happening - they will not be spoiled by others' help!
Don't try to "do school" until the babies are sleeping through the night, unless they are completely independent, and it's not keeping them from helping with the household needs during that time. Make up a schedule for after the birth with all necessary chores assigned. Don't try to get creative - assign them the basics they've reasonably mastered and give the same children the same tasks for the duration. If they are doing the same things at the same times each day, this will cut down on the number of reminders that will be needed. There will be time for variation later! If some of the children work better together, assign them together. If some do better widely separated - keep them separate. You want this to be as workable as possible. There will still be plenty of opportunities to learn character and to get along with each other without going out of your way during this high-stress time period to set them up! Assign older ones to keep the younger ones on track, including helping them at mealtimes, pottying, toothbrushing, reading aloud, having them pick up after themselves, dressing them, etc.
For instance, right now my oldest son is in charge of laundry Monday to Wednesday (the girls fold and put away) and my second son is in charge of our 2 1/2 year old those days. Then Thursday to Saturday, they switch tasks. This is, of course, in addition to their other daily chores. My third son is gifted with growing things and he does lots of our outside work. I don't combine children for kitchen clean-up - the same child clears and wipes the table, sweeps the floor, empties the dish drainer, and stacks and wipes the dishes. Right now my younger daughter does breakfast, my older daughter does lunch, and my third son does supper.
Take your thank yous as seriously as you should take your need for help. Thank everyone specifically and sincerely for whatever they put into your family during this time, no matter how small. If you neglect to do this, they will feel taken advantage of, even if they told you not to write a thank you note. Do it anyway! I kept a running list of anyone who helped, with their address and what they did for us, meals, gifts, etc., with a box in front of each person that I checked off when the thank you note was sent.
If you can find out the babies' genders ahead of time, this can be a huge help in preparing, as you won't be forced to find appropriate clothes before you feel ready for it, which may be later rather than sooner! My previous boys had not left much behind them, but we got all the clothes ahead of time that we needed for the twins' first 6 months (plus a start on the next size/season), and I was so grateful for this later! Before they were born, I went to one great "twin yard sale" and all my trusty thrift stores! I got some matching sets for public appearances, as our boys are not identical, but mostly we just needed more boys' clothes. We don't have wealthy or spendthrift friends, and the gifts we received would not have been nearly sufficient. If I'd had a boy and girl, what I had stored away would have been enough, I'm sure.
I am wondering if you are planning a home or hospital birth, and how prepared you would be for a C-section. I developed pre-eclampsia (thank the Lord it was not severe, and not until near the end, hence the bedrest to keep it under control) and both twins were solidly transverse from at least 32 weeks on. After six homebirths with our wonderful midwife, the twins were born C-section. This was very hard for me emotionally later on, as I hadn't really accepted the possibility personally. It would be wise, even if you are planning a home birth, to have everything ready in case you need to transfer to the hospital.
One more thing:
My first and strongest recommendation unless you're in the last month or so of pregnancy is to get a copy of Dr. Barbara Luke's book on expecting multiples, and one of Elizabeth Noble's book, "Having Twins." (I liked the older edition of the latter book better - the newer one had weird stuff in it about pre-birth memories.) Many twin books emphasize the time after the twins are born, but these two have tremendously important information about having a healthy twin pregnancy that you really need to have as soon as possible. An acquaintance with 2 year old twins (# 9 and 10 in the family) gave me the Dr. Luke book. When I found out twins were on the way, I remembered her twins were born at term, and both were over 7 pounds, and that she'd followed a special twin diet, and when I called and asked her what specifically she'd done, she wanted me to have her copy of this book! At my 6 week post-partum check-up, I bequeathed my copy to my midwife, then regretted not having it to loan out, so I bought another one. I would be happy to loan it to you if that would help you, and you could keep it for the whole pregnancy. It tells very specifically how many servings of each kind of food you should get every day, according to which trimester you're in. My son made up slips of paper for me with each food category and space for my tally marks, and I used one a day to keep track of my servings, then threw them away. There are several helpful charts in the book that you can photocopy. The actual food choices they recommended were not as healthy as what we eat (especially with white flour and refined sugar), but knowing the servings of the different categories were so helpful, as was so much of the rest of the book. I tend to put off eating as the least important task in life. I know I would have fallen far short of what would've been good for the babies without that practical information. Since we don't have a large income, my diet was less varied than I liked, and I got very tired of eating by the end! BUT I felt fully rewarded when I saw those healthy boys! The dr. said I was 37 weeks 1 day when they were born, but I know I was actually 36 weeks 2 days. (You know how those things can go.) The boys weighed 7 lbs. and 6 lbs. 13 oz. Your goal is to grow the babies to the same healthy sizes they would be if you carried them one at a time. There is no genetic reason twins are almost always growth retarded - it is caused by insufficient diet and the mom not getting sufficient rest, and burning off what should be going to grow the babies. I gained more weight than they said I would on that diet, but it was almost exactly what my friend had gained, and we both lost it all by six months postpartum - nursing two really helped!
It is more important than you can imagine right now that they are born as close to full term as possible. Caring for infant twins is enough of a challenge when they are born healthy and strong at full term, and adding any complications such as insufficient outside help, heavy responsibilities toward other children and the general household, NICU stays, nursing difficulties (common when babies are even a little early), insufficient preparations (including needed supplies and organized-ness) for the realities of caring for them, C-section recovery, etc. etc. can quickly make the situation completely overwhelming. One of the mistakes I made was that I REALLY didn't think I would run into any of these problems - they're for other people, and I didn't read those sections of the books very carefully! We didn't face all those difficulties, but we did face some of them. But somewhere early in the pregnancy, I realized that I simply could not use the excuse that I was too busy to rest properly or was tired of eating properly, because the two most helpless and needy people in the family were depending on me to take this seriously, and put a priority on caring for them. It was hardest in regards to my toddler, still a baby himself in many ways. But he and I cuddled a lot with me resting on my left side and reading to him, and he got more of me that way than he might have if I was my usual busy self.