Hi A.,
My daughter turned 2 and a day later, my twins were born so I had 3 kids under 3 for 364 days!I don't remember much that I did to survive (they are 9 and 7 now), but I do know that I worried myself sick for no reason. Yes, it was amazingly tiring but we handled it and it wasn't nearly as bad as I imagined it to be. So my advice is try not to worry too much and enjoy your beautiful babies.
Okay, a little practical advice would be just to be sure you get a routine where you know when you will get rest. For example, every morning after the morning crazy feed finishing about 6am, my husband would be responsible for the kids as I got an uninterrupted nap before he went to work. That gave me the peace of mind I needed to get through the day.
Also, I remember having a special basket full of my older daughter's favorite things and new things thrown in here and there to keep her occupied whenever I would be completely preoccupied with the babies.
I also remember having diaper bags completely packed and ready to go at all times except for a few last minute fresh things that I had a list of and knew by heart very soon.
Good luck! It's hard, but amazing, just like your beautiful kids. I hope you have lots of help. Be so relieved you are ALSO not planning to go to work!! (I know, you'll be at work all right but at least it's the most important job in the world!)