Hello
Last time we went our two DS were 4 and 18 months, and we had more of a problem going out than coming back . It took the first 5 days before they would sleep past 4.30pm, and DS (4) would crawl into bed when we got back to the room at 5, and fall asleep!
In a way it worked out well, as we were on site, so we used to get up at 4.30, go for breakfast in the deserted ASmo food court when it opened at 6am, get the first Disney Bus at 7am to whichever park had Extra Magic Hour that day, and get on all the rides before most people were up.
Then when they were both asleep by 6pm, we would watch mad tele for a bit then go to bed ourselves. Having had no proper sleep for 4 years, it was the best thing in the world; they would both sleep through. LOL.
By the second week they had adjusted so we could go to the fireworks etc.
Coming back we had a 9pm Virgin flight. They both slept all the way; we didn't! They then slept all the way home in the car, and were back in the normal routine that night.