Hi there, Rochelle!
How wonderful it is that your mother is willing to make the trip to Walt Disney World; it does bring so many smiles! Now, while I can in no way determine if lines and walking would be too strenuous for your mother, I would suggest that you look into getting a Guest Assistance Card for her.
The Guest Assistance Card offers Guests with special requirements the help they need to enjoy their trip in comfort. This might mean special handicap-accessible access to rides, a shady spot to wait, a Cast Member escort through a line, or whatever the Guest Relations personnel feels would best benefit your mother's circumstances.
When you arrive at your first Park, head right towards Guest Relations. Your mother should have with her a note from her doctor on letterhead describing the best way to work with her recovering body; this will ensure that she receives the proper level of Card. She should also be prepared to explain any other requirements she might have that are not listed. While she will advocate for herself, backup from a medical professional will definitely solidify her request.
The Guest Assistance Card will be good for the duration of your trip, and will allow up to six people in the traveling party to accompany her.
While you are preparing for your trip, make sure to check out
Disney's resources for Guests with disabilities. This page will help you all pre-arrange as much as possible to ensure your mother's comfort and ease of travel - a room on the first floor, close to the bus stop, etc.
Have a wonderful, comfortable time!
See you later, celebrator,
-Deborah B.