We stayed at AKL when my little guy was 13 months old! It was an amazing trip. We really loved it there. He just adored all the animals!
In our room, there was a space beside the TV cabinet that was just right for a pack and play.
Honestly, we didn't really have any sleep issues - but I should say that Paul is a pretty easy sleeper and we never stuck to a schedule that was strict.
Most of his naps were just in his stroller. He was a great sroller napper. Sometimes we would go back he AKL to swim and then we would all three take a nap together, so no problems there.
As for night time, we honestly all tended to go to bed at the same time. Paul is a night owl anyway and he stays up late at home. We would usually go out to see Wishes, Illuminations, etc. and then all come home and crash at about the same time. Sometimes, he would fall asleep on the bus ride home and we would just strip him, change his diaper (all without waking him up) and plunk him down in the pack and play, with a plan to shower him off the next morning. A few nights, we would put him down and then sit out on the balcony for a while watching the animals. It was heaven! (Especially when we stopped by Mara to pick up some Zebra Domes on the way up to the room!) Once or two nights we even put him in the stroller, wheeled him around the resort until he fell asleep, and then parked the stroller by the hot tub while we enjoyed a little relaxation time. Most nights, though, we all went down together.
Paul's 2 1/2 now, and he's been to Disney World three times since that first trip - and we're headed back in December. What I described above is still pretty much how we do things. Like I said, though, it probably wouldn't work for a baby who needs a strict schedule, early bedtime, absoute quiet while sleeping, etc.
I would imagine that your DH and older kids could find plenty to do around the resort, though,if you and the little one need to turn in early - night time animal viewing from the observation areas, swimming, storytelling at the firepit, etc. There's always lots to do there! They could even head off to a park for the later part of the evening.
Have fun!