I thought that anyone with an "adult ticket" could take someone with a "childs ticket" on the ride... My experience is when I took my 2 kids to Animal Kingdom, by myself, a summer ago they wanted to go on rides that I wouldn't go on. I walked through line with them & the CM's would let them go on without me because she was 10, my younger son was 7. The CM's would usher me where to wait for them at the end. We did that all day with no issues and yes, CM's did ask the ages.... I don't know the official age rule, but that is my experience.