Last trip was just myself and my 3yr old DD. We stayed in a studio at the AKV where she slept on the sofa bed and I on the bed (they are right next to each other is these rooms). Had no problems with her falling asleep and staying asleep. Like many have said, she was pretty tired by the end of the night (if she made it back to the resort awake) where sleep wasn't an issue.
However, even though sleeping isn't an issue in a regular room we still prefer staying offsite in a suite so just we can put her in the living room to sleep and we can stay up with the lights/tv on the bedroom.
You can get a suite offsite for nearly a third to half the price of what Disney charges for a AoA suite depending on season.
For our trip next year the room only cost for 7 nights is:
Art of Animation Suite: $2,314
Buena Vista Suites: $858.38 (Another $40 gets you a king bed and a whirlpool tub)