Hello, Debra,
Star Wars Weekends is HUGE with my family, and we've been attending yearly for many years now. To help with your planning, I went back and looked over the Guide Map from last year's event and didn't see any area indicating an area reserved for wheelchairs and ECVs. However, that doesn't mean there isn't one.
I would encourage you to stop by Guest Relations at the park to inquire about a special location. If there is not one, my favorite spot to watch the is right outside the exit of Keystone Clothiers where it is shaded. Since this is closer to the stage, it can be more crowded. If you are okay not seeing the stage show, you may find being near the first entrance of Mickey's of Hollywood a good spot since that is where the motorcade starts.
I'll also share with you that last year the "Legends of the Force" Motorcade and Celebrity Welcome parade started near the park's entrance then moved down Hollywood Boulevard. Following the celebrity welcome on the stage, the motorcade returned back down Hollywood Boulevard toward the entrance. At this point, a large portion of the crowd had dissipated. I then was able to move from the back of the crowd right to the front where I was able to then clearly see all of the celebrities very easily.
May the Force be with you!
-Kara