Hi Heidi!
I have a son with Cerebral Palsy who uses a stroller as a wheelchair. While you're at Guest Relations to get your son's Disability Access Service (DAS) Card, be sure to tell them he'll be using his stroller as a wheelchair. They don't note that on the DAS but will give you something to go on his stroller so that Cast Members (CMs) know that he's using it as a wheelchair.
For those queues that require Guests in wheelchairs to enter through alternate queues, you can see a CM for assistance. They'll give you a return time to come back to the attraction based on the current wait time and no DAS is required.
Disney World is a great place to visit for Guests with 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.
I'm limited in space but answered a question with
details of how the DAS works that may help you.
If your son has any comfort items, bring them if possible. If he has head phones or ear plugs to help keep the noise level down, bring them. If he become anxious, remember the things you do at home to calm him down as keeping it familiar sometimes helps (like singing). Remember to relax and breathe. Sometimes you may just have to take a break until he calms down and try again later.
Here's a list of
Frequently Asked Questions about the DAS.
Wishing you minnie magical memories :-) Allison V.