Travel with a Younger Elementary Schooler (ages 6-9)They'll likely remember much of the trip. They'll have stamina for a full day. Most rides are accessible to them. They're unlikely to be jaded about the Disney experience.
That's an enormous distance for a 4- or 5-year-old to walk, and if you decide not to take a pushchair to Disney World, you might do a lot of carrying. You will likely be walking around from very early in the morning until late in the evening. That's a lot for even the best four or 5-year-old walker.
No, Disney does not expect you to bring any proof of age for children under 3. The honor system is pretty easy to follow at that age, so you are good just arriving and having a magical time.