I think the best way to approach a possible visit is to speak with your son's teachers, aides, doctors, etc. to determine potential issues.
Depending on your son's age, and his triggers, you could consider a stroller as a wheelchair, which would allow him to stay in his safe space (perhaps with a blanket to block external stimuli). Ear Protectors are another good idea if he is bothered by loud and constant noise (WDW is very noisy!)
Storyboards may help, again, based on his needs and his age.
You could also consider going at a less busy time--honestly, nowadays, that seems like never, but maybe avoid Spring Break, Easter, Thanksgiving week, and Christmas--the crowds are absolutely insane at those times. Depending on how much heat he can tolerate is another factor.