Hi April,
Sounds like you are planning an awesome trip! Disney has manual wheelchairs & ECVs available for rent at each of the four theme parks. Wheelchair rentals are available at Downtown Disney as well. Click
here for a list of rental costs & locations. They are limited & depending on what time of year you are traveling (Christmas is generally busy), they may run out early. Advanced reservations are not accepted - they are rented on a first come basis.
Wheelchairs & ECVs cannot leave the park from which they were rented. If you rent an ECV or wheelchair at one park & hop to another park the same day, you'll need to retain your receipt to show at the next park to get another wheelchair or ECV - if there is one available.
If you'd like to guarantee that you will have an ECV or wheelchair at the parks or need assistance outside the theme parks during your trip, you may want to consider renting one from a vendor in the Disney area. There are several vendors who cater to visitors to the Orlando area.
If your Mother has never used an ECV before, they take a little getting used to - especially in crowds like at WDW. I'd suggest going to a store that offers them for customers & practice. It will make things go a lot more smoothly once she is at WDW.
There are some attractions that she will be able to remain in a wheelchair or ECV to enjoy. Others require that guests transfer to wheelchairs. There are some attractions that require guests to be mobile to board the ride vehicles. For a list, visit the Mobility Disabilities section on the WDW website by clicking
here.
Wishing you many magical memories :-) Allison