My daughter with lower functioning ASD, she is now 9 years old, has been going to WDW since she was 13 months old. There are certain rides we will never do with her and they include Space Mountain (because she would have to sit alone in a seat), Tower of Terror and Rock n Roller Coaster. She isn't too fond of dark rides/attractions but does okay in Pirates, Haunted Mansion, Peter Pan, Soarin' but absolutely hated Dinosaur and It's Tough to Be a Bug. I think it is about prediction and there really isn't a simple way to prepare her for those two attractions. I know your son is still very young and probably isn't tall enough for many rides but this is the list of my daughter's very favorite attractions in no certain order: Exhibition Everest, Test Track, Big Thunder Mountain Railroad, Dumbo, Aladdin Magic Carpets, Splash Mountain (although she clings to us during the big drop) the parking lot tram (yes!), the monorail and the ferry from the TTC to MK. She has an iPad and we have loaded attraction photos into the app ProLoQuo2Go so she can make choices and to tell her what we are going to do next. If she REALLY likes an attraction she will repeatedly sign "more, more" (she is non-verbal) when it ends. We rode Exhibition Everest three times in one day because she communicated to us "more" and we want to reinforce her communication but I just about threw up afterwards from motion sickness! But I will do anything for my DD when she successfully communicates with us.