Our daughter just turned 4 during her first trip in march 2009. We did alot of research on height requiremtents. She is very tall for her age, so she didnt miss out on much, however, there were things we didnt let her go on because although her height allowed her, we felt her age didnt.
Last year she was 5 when we went in February, and since she did so well on things like TOT when she was 4, we let her go on Expedition Everest. It happened to be raining, so the water felt like needles hitting your face, so she did not want to go on again.
This year when we go in October she will be 6. She is now tall enough for Rock n Roller Coaster, which she is extremely excited about. I told her she could only go on RRC if she was brave enough to go on EE.
So, in short, (or 3 paragraphs LOL) I agree with those that say let them go on what is comfortable for them. While our daughter is brave when it comes to the coasters, she is still telling me she WILL NOT go on Dinosaur again this year LOL. Happy Travels All!!!