I don’t know if this is still true but in 2009 my son needed a wheelchair following knee surgery just prior to WDW trip. We were planning on renting a manual chair at the parks but our resort- POR, gave us one to use instead. We got to keep it until check out and could take it anywhere. Best part was that it was free!
I don’t believe you can reserve them ahead of time so they are first come first serve but ours was actually delivered to us from a neighboring resort after we requested it at the front desk.
We found the manual wheelchair for our 16 year old just as easy to push through the parks as the double stroller our toddlers were in. Plus since he could get out and walk some with his crutches the fact that the chair folded made it so much easier for crowded buses, etc.
Definitely check out to see if this is still an option.