Welcome to the Disney Parks Moms Panel Brian!
I am so thrilled to hear that your son is in remission! Sounds like a trip to Disney World to celebrate is a wonderful idea!
Disney World is a great place to visit for Guests with Special Needs. Because your son tires easily, a Guest Assistance Card (GAC) may be helpful. The GAC would assist in allowing your son & up to 5 other members of your party to access some attractions via an alternate queue that may provide more shade or reduce the wait time in the heat.
To request a GAC, visit Guest Relations at the 1st theme park you visit. Explain your situation to the Cast Member so that they can tailor the GAC to your son's specific needs to the best of their abilities. You likely will not be asked but it wouldn't hurt to have a letter from his doctor just in case.
If you feel that your son ever needs a break, do not hesitate to visit a
First Aid Location. There are locations in all of the theme parks and water parks and they will welcome him there.
I have a son with Cerebral Palsy that is sensitive to heat so we're used to dealing with that at Disney World. I answered a question for another Guest giving him some
suggestions on staying cool at Disney World that I think you may find helpful as well.
Please feel free to visit with any other questions. We're hEAR to help!
Wishing you minnie magical memories :-) Allison