Housekeeping may have aids in store that will help if you have mobility problems.
I always ask for bed boards, because a stiffer bed is easier to get in and out of.
I always ask for a raised toilet seat which housekeeping keeps in store.
Off site medical suppliers can provide more than just
ECVs. Last trip I rented a wheelchair with a commode seat from Walker Medical, to use in the shower. - my power wheelchair doesn't like water!
AKL, Polynesian & GF have zero entry pools with special wheelchairs that can be ridden into pool. (AKL & Polynesian are definite - haven't checked for certain at GF). Many (but not all) of the pools at other resorts have 'bump staircases' that let you transfer from a wheelchair to the pool if you have good upper body strength.
If you are staying at a resort without a zero access pool or other suitable means of access for your needs - pool hop to one that does. Ask first to be certain, but I have been told that in the case of 'disabled' circumstances, an exception to the 'no pool hopping' rule is likely to be made.
If you want to get 'offsite' with a wheelchair, remember that all LYNX buses (Orlando's public transport system) are wheelchair accessible, though you do need to get to TTC to get one.
Also- The cab company that serves WDW has a few wheelchair adapted vans. The parking valet at the entrance will be able to call one for you.
Also - Mears bus service proviide wheelchair vans to & from the airport, Sea World, Universal International Drive etc. They will pick up & drop off at any Disney resort.
Andrew