Hi Veronica ~
I love that you're planning ahead for your Mom. My son has Cerebral Palsy and has a very difficult time boarding and getting off of attractions especially as he has gotten older and bigger.
The Walt Disney World Resort has done a good job of providing
services for Guests with mobility disabilities. It sounds like your Mom may benefit from
renting a wheelchair. They are available at all of the theme parks, water parks, and Disney Springs. That will help her with stamina as the parks are really big. Most of the attraction queues are able to accommodate Guests in wheelchairs and ECV's. If your Mom will need physical assistance getting on and off attractions, remember that someone from your party will have to assist her.
Disability Access Service (DAS) is designed to assist Guests who are unable to wait in a standard queue for medical reasons including those that are not apparent. If you feel that your Mom would be unable to wait in a queue, please stop by Guest Relations in the first theme park you visit to discuss her specific needs and ask for assistance. Here is a link with some
details explaining how DAS works.
On the link I've provided regarding mobility disabilities, there is a list showing which attractions will allow Guests to remain in a wheelchair and which ones require Guests to be mobile to enjoy. I am limited in space but please visit me again and let me know which parks you plan to visit, I am happy to give you a list of attractions in those parks that may be difficult for your Mom to board.
Wishing you minnie magical memories :-) Allison V.