1) There are places to view that have chair or ECV access.
2) But, get there 1-1½ hours early, as they fill up quickly.
3) Additionally, they usually only allow on person to accompany the chair/ECV, so others can view from the area.
4) If they allowed the entire family, it would fill u too quickly . . . human nature is to take advantage of the system.
Quite honestly, I found I was able to watch everything from the hub without too much trouble - just don't go into the section nearest the castle as that obviously gets really crowded. You can even watch things from near the restrooms near Tomorrowland Terrace! Okay, there are a few trees here and there, but if you can position yourself back from the crowds you'll get a good view of everything (and you won't feel claustrophobic from being surrounded by people standing up).
Last year I drove my ECV right up to the wall on one of the circular raised 'garden' sections so no-one would be able to stand directly in front of me and block my view and I got a great view with only a few branches to mar it.
I have been up there a few times some times you can see about 80% of it and some times you can see less I think you will have a better chance of seeing if you can stand during the show.