Hello, Terry!
Welcome to the Disney Parks Moms Panel. My son has
mobility issues that require assistance touring the Walt Disney World Resort. We bring my son's push-stroller, so he is comfortable and feels secure. I always visit a theme park Guest Relations Lobby (on our first day) to secure a tag for the stroller that identifies it as a wheelchair. This tag is good for the length of our vacation and allows him to remain in his stroller in attraction queues.
Only adult-sized
Wheelchair Rentals are available in all four theme parks, Downtown Disney Area and Walt Disney World Resort Hotels. They are available on a first-come, first-served basis and reservations are not accepted. It's also important to note that a rented wheelchair must remain in the park in which it was rented.
If you decide that you want to rent a wheelchair for your granddaughter, consider contacting a Disney featured provider. These companies offer a variety of wheelchairs and ECV models. You can find a list of Disney featured providers at the bottom of the above-linked rental page.
I hope this helps to answer your questions. Please let me know if I can be of further assistance. Wishing you and your granddaughter loads of pixie dust during your vacation.
Missy