We never go back for naps either...the adults didn't need it and our daughter who was 1 and 2 when we've been there the past 2 years fell asleep in the stroller right before the parade. I think you pay too much to get into the parks to spend 4-5 hours traveling back and forth back to the hotel (walking, parking/catching a bus, trams, etc.) and then getting back to park and getting settled into your groove again. If you have a reclining stroller, just give them whatever they need to go to sleep (bottle, cup, blankie, etc.) and after walking around for about 10-15 minutes, they should fall asleep.
As for nighttime sleeping, what we did was give them baths at night when we got back after the parks closed. The older one was in first (he was 4 and 5 at the time) and then he had time to wind down while the younger one took a bath. We showered in the morning before the kids woke up.
As far as sleeping arrangements, you can push in the mattress (maybe the whole double bed...I can't remember) against the wall next to the bathroom and the 2 year old could sleep there along with you or your husband. Then the parent could either continue to sleep there with the 2 year old -OR- you could stack a ton of pillows on the side of the bed and hope he doesn't roll over and fall out.

I would definitely get a crib for your younger child. If they were to fall off the bed, it is pretty high up and they could be hurt badly. But I think it would be too crowded in your room at ASMu with 2 cribs and both beds.
Your ADRs should go well....character meals are best, but regular sit-down restaurants can be done. We took ours to the Coral Reef and they both enjoyed it. Just remember to bring some small toys (even happy meals work well), have a small snack because at non-buffets, the food can take a while to arrive. Plan on spending 1 to 1 1/2 hours at each sit-down meal. Always use the bathrooms at the restaurants because they are usually pretty clean and always easier to find than the ones in the parks. Also, you're already there so may as well have everyone try. If you have any character meals, try to discourage the characters from sneaking up behind your children and tapping them on the shoulder...one did to my 1 year old and she was afraid of the characters for days after that!
Any other questions, just ask. Good luck! We have gone in December the past 2 years but are going for free dining this year so it should be a different experience!