Hi Audrey ~
My son has Cerebral Palsy so I completely understand the challenges of traveling with a special needs child. We were at the Magic Kingdom last week and saw Happily Ever After. It really is an amazing show and takes WOW to a whole new level. Being in front of Cinderella Castle is where you need to be to see the projections.
Unfortunately, I did not see any special sections for Guests in wheelchairs to view Happily Ever After. There are special areas for the Festival of Fantasy Parade but unless they change something there is no special viewing for the fireworks.
I have a couple of suggestions for you. Go early and get a spot along a fence in the hub in front of Cinderella Castle. If you position your son just behind the fence, no one will be able to stand in front of him and he will have a better view. There is also a fence near the Crystal Palace that you could try if the hub is filled. Get down on your son's level to see what he can see from his chair.
Another suggestion is doing a
fireworks dessert party. You can do the dessert party with a terrace view or a plaza view. The desserts are the same for both parties but the viewing areas are different. The plaza view is in one of the garden areas behind the hub and it is all standing with no seating. There is a fence there but Guests can stand in front of it on the other side. The terrace view is a little more expensive and you don't get a clear view of the castle but it may be better for your son than sitting in the sea of Guests. You are welcome to move within the area to see the fireworks and we found a spot with a pretty good view for my son.
You can also check to see if the area on the second level of the train station will be open that evening. If so, plan to get there super early for a good spot.
Wishing you minnie magical memories :-) Allison V.