There are wheelchair viewing areas for Illuminations. They are marked on the park map. They are by Germany, by Canada and one area on each side of the Showcase Plaza.
We don't usually bother with them since they tend to fill up quickly and are often quite crowded (not things that DD will tolerate). They will allow up to 5 members of your party into the area, but the area right along the fence is reserved for wheelchairs, scooters. So, if you have small children, you are not able to park your stroller along the fence. If it is busy, they will limit to the person with a disability plus one other member of the party. When we used the area over Spring break a few years ago, we were told that our whole party (total of 5 people) could be in the area, but if they needed the space for more people with wheelchairs, all but one person with DD would have to leave. That trip, DD ended up parked behind a tree and couldn't see anything, so after that, we ussually just stake out a spot along the water someplace else.