Hello, Tina,
Having traveled to Walt Disney World with my mother who is in a wheelchair, I have always been so impressed with quality of care and services available for her so that she can be part of all magic and joy. Rest assured, there are preferred viewing areas for the parades as well as Illuminations at Epcot. You'll want to make sure and get a park map when you arrive. Look for a small red box with a white P and a picture of a wheelchair on the map; these are the preferred spots. You can also ask any cast member to point you in the right direction.
You won't be able to make reservations for the spots, and they can fill up quickly. You also will be limited to the number of guests that can accompany your grandmother.
If you book the Fantasmic! Dinner Package, I would include a notation in your reservation about having a guest in a wheelchair. It may also be worthwhile to still try and arrive on the early side to see Fantasmic! just to be safe since not all guests who may need preferred seating may have included that on their dining reservation.
I thought you may also like to read more about traveling to Walt Disney World with
Guest With Disabilities to learn about further services that are available.
Have a wonderful trip and please let us know if we can help again.