Your three year old will be cured. Go early, but return to the hotel around lunch time, take them for a swim and have a nap. Go back and stay until the kids are ready to sleep, probably later than their usual bedtime. They will sleep like rocks and so will you. Repeat for a couple of days.

Oh, get a stroller, even for kids that are older than normal for a stroller. Lots of walking. If they get tired, they sleep right in the chair.

Meltdowns happen when you leave. Until then it is all magic kingdom.