My DD will be 2 weeks shy of 3 yo when we visit in June, so I wasn't planning on purchasing park tickets for her. Will I need to provide proof of age upon entering the parks, or do they just take your word for it?
Probably wouldn't hurt to take along a copy of the birth certificate if you have one. That might give you some peace of mind.
But every posting that I've ever read on these boards indicates that CMs will NEVER challenge the age of a guest. I doubt they would fall for a 20yo trying to use a Child's pass, but they do not stop people and question the age of those who appear to be near the 3 and 9 age break points.