My son Danny is 4, but he's just over 40 inches. I can guarentee you that he would ride and would ride with joy - probably with his hands in the air the entire time. He rode the Lakeside Cyclone (which has, by the way, VERY minimal restraints) 25 times in one evening when he was just 2 years old. He had his hands up every ride. If he can ride the Cyclone, which is not, shall I say, real smooth, MF, with it's ultra-smoothness wouldn't be a problem at all!
Alas, when we hit the Point this weekend for two days, he will be restricted to Jr. Gemini and Woodstock Express. He likes 'em both, but I wish he could ride more - at least CCMR or Disaster Transport!
Daryl