Welcome to the Disney Parks Moms Panel Marlen ~
You are smart to plan ahead. The parks are big and it may wear your little guy out really fast.
Disney offers
stroller rentals and wheelchair rentals for Guests. I am not sure what size your son is but the double strollers can accommodate up to 100 lbs. Depending on your son's height, that may or may not work for him. You can see pictures of the strollers on the website AllEars.net.
The
wheelchair rentals in the parks are the standard size and they do not have smaller wheelchairs for children but I see lots of Guests with their children in them and they seem to do fine.
I have a son with Cerebral Palsy and he uses a special needs stroller as a wheelchair. There are several private companies in the Disney area that rent strollers including special needs strollers. OrlandoStrollerRentals.com offers a Liberty Push Chair that can accommodate kids up to 100 pounds. It may be more comfortable for your son than the hard plastic ones for rent in the parks. If you are staying at a Disney World Hotel, they will deliver and pick your stroller.
Disney is committed to assisting Guests with all types of special needs including those with
Cognitive Disabilities. They have put together
A Resource for Guests with Cognitive Disabilities including Autism Spectrum Disorder (ASD) which you can find on the link shown above. This will give you a lot of things you can do before and during your trip to help it go as smooth as possible.
Please feel free to visit again with any other questions. We're hEAR for you!
Wishing you minnie magical memories :-) Allison V.