check out Kelly Monaghan's book - Universal Orlando; a great source for the 1st time visitor esp as to ride descriptions, etc. The detailed reviews will give u a handle on whether ur son would enjoy them or not
ruling out dark & thrill rides eliminates alot of attractions at any theme park, even MK...a though one. Is he wary of being in relative dark as in a pre-show?for that consideration i voted no
If he can handle Peter Pan/Snow White/Pooh perhaps ET; and surrounding kiddie rides - Barney Show, woody coaster should appeal to him; along with shrek & jimmy neutron.
At IOA, Suessland & the dinosaur adventure area (name escapes me) and kiddie coaster
my youngest DS has older bros & was exposed to Jaws, Terminator, MIB, The Mummy, Spiderman, etc. at an early age via movies so it wasn't a factor for him.