I agree: click on the DISAbilities Board, there are lots of people there who can answer your questions.
You never know if your son will hate rides that have a Disney "twist", maybe you will be surprised. We have taken our 20 year old autistic son to WDW 14 times, and it's hard for us to think that he would enjoy any other vacation. The rides at WDW aren't too wild, with the exception of a few roller coasters, so there will a lot he will enjoy.
Read up on how to get and use a GAC,Guest Assistance Card-- it is a life-saver for us. Also get familiar with FastPasses, because this is how the rest of your family can navigate WDW without your autistic son.
I hope you are pleasantly surprised and you have a great trip.