I was in the same situation 4 years ago, but luckily it was with my first baby, so we didn't have another child to be looked after, and we weren't QUITE as strapped for cash, as we wouldn've been 2nd time around. It IS very hard to stay on bedrest and follow orders, when you feel like an invalid and like everyone is doing everything for you/the world/your life is passing you by, and you may not feel physically like you have anything wrong with you, and you could just do stuff on your own - DON'T DO IT. Make sure you stay to Dr.s orders, it is important, and let them help you, they love you and this coming baby and want the best health for you both.
There will be plenty of opportunities in the future to pay it back to them through favors and pay it forward to others in similar postions. Also like everyone else said, write them each a heartfelt letter and tell them how much what they have done means, and that as soon as you recover and get in a routine with the new baby, you will be hapy to pay them back with any kind of help you cna give them.
In the meantime, I know you wantot give something back, and I rememeber how it was to be stuck in bed all day, bored stiff....One thing I wish I had done at the time, and would do now if I was in that situation - take up a hobby like crocheting or knitting, that you can do in bed, easily, which is fun, interesting/occupies your many boring hours in bed, and can make gifts for others! I do crochet now, in between taking care of 2 pre-schoolers, but i just dream of what I could've gotten done then with 3 months of bedrest on my own, with no-one to distract me, LOL!
There are lots of easy patterns, free online, and in books from the library, you can learn to crochet from books and videos from the library, and then make everyone something. Yarn isn't too expensive, either, and you probably only need an H sized and/or I sized hook,a nd whatever Yarn is on sale. You can make winter hats, washclothes and towels for the kitchen, hotpads, scarves, cute little purses, stuffed toys, baby clothes, socks. slippers, and learn a new skill at the same time - they say skills like knitting and crochet help ward off dementia and alzheimers if you keep at them as you get older, bonus!
Good Luck!
Jessie
P.S. Call your local public library and see if they will deliver books ot people in your position, many will.