D.Y.
First of all - you are awesome for nursing those babies! If you were in front of me I'd give you a high five. :)
My advice is to rotate co-sleeping at night. So when one baby wakes up, bring him to bed with you until the next wakes up. When that happens, enlist your husband to get the other baby to sleep in their crib and you get to work nursing the other baby. Lather, rinse, repeat! Hopefully this helps.
Do you have side-lie nursing perfected? If not, do so! It has saved my sanity and I have a singleton.
Do not give your baby formula or expressed breastmilk in the night! If you do that, your body will think it doesn't need to produce that milk for that nighttime feeding. It can have a serious affect on your supply, and since you're nursing twins the last thing you need is to give your body the wrong signals. Plus, nighttime nursing has proven to be an important factor in delaying your fertility. Lots of bonuses!
Good luck, mama!