Just got back last night from 9 days at the parks. Son will be 5 in June and did Soarin' and LOVED it. He also did Splash Mountain, Thunder Canyon, and Tower of Terror (twice on each of these).....and I thought he would have been scared to death of these things! Boy was I proven wrong!!
Soarin' is the tamest of all these rides. You just sit with your feet hanging down and it feels like you're moving, but you're hardly moving at all really. Can't remember the height restriction, but he's around 44". Also, the smell-effects are great! Have fun!