One more thing I thought of .... if you still have it, bring your stroller. If you don't have, get a cheap umbrella stroller from target. They come in SOOOOO handy at the airport because its a lot of walking. When they want to walk, the carryons go in the stroller and we gate check them.
The strollers are also SO handy for port days, if you want to walk around and shop. Usually they are so exhausted, they get a great nap while we shop. My daughter is a tall four, and in a few months, I'm sure she will look really odd in her stroller, but I don't care. We paid a lot of money for our umbrella strollers, so I'm keeping them at least until our next disney trip.