don't forget, in universal studios, there is the ET ride. think you're son would enjoy that....also shrek, as you get to meet them afterwards....not really sure he'd like earth quake or twister, but that's just me. it's very loud in there...and sudden actions. as for IOA, try the flying ride in jurrasic park, and the flying unicorn is brilliant for younger kids (as it's such a short ride) the shortist i actually know. i will write a list of atractions to avoid, if this will help you.
let me know