Hi Maryann,
WDW is AMAZING for Guests w/ special needs. If your son uses a stroller as a wheelchair, there are a couple of things you need to help facilitate this. When you are at Guest Relations getting the Guest Assistance Card, tell them that he uses a stroller instead of a wheelchair. They'll need to stamp the GAC to indicate that "Guests can use their stroller as a wheelchair" in addition to the "Guests can use an alternate attraction entrance, where available". Be sure to obtain a red band to put on his stroller. Make sure you put it in a location that Cast Members can easily see - I put it on the handle.
If you don't have the stamps & band, you will be asked to park the stroller in designated stroller parking areas for an attraction. If your son uses a wheelchair, the GAC stamped with "Guests can use an alternate entrance, where available" should be all that you need.
CMs at some attractions may ask you if he can transfer & if he is able to stand for a short time. If so they will ask you to leave the stroller or wheelchair near the exit of the attraction & escort you to the alternate entrance. Be sure you park it where they tell you - otherwise you could return to find that it has been moved to the regular stroller parking area. Check out the Guests w/
Mobility Disabilities section on the WDW website.
If your son has any medications that need refrigerating, you can put them in a small cooler & Guest Relations will be happy to hold them for you. If you have any special dietary requests, be sure you mention them when booking ADRs. If its hot & your son is heat sensitive, stop by any first aid station & ask if you can let him take a break. I am happy to answer any additional questions. Wishing you many magical memories :-) Allison