Hi and :

to disABILITIES!
You do not need anything to rent a wheelchair (except money). If you click on where it says "disABILTIES" at the top of this page it will take you to the Index. One of the top items is the "disABILTIES FAQ" which will gives lots of useful information. Post #2 gives information about wheelchair and
ECV rentals. We do tend to recommend that you rent from an off-site locations as (a) they tend to have better/more comfortable items, and (b) the chair or
ECV is available at all times, some of the Resorts have very long corridors.
Or, if you want an easier route, click on the link in my signature.
Most of the attraction lines at WDW are "mainstreamed", so that a wheelchair or ECV will remain in the regular line until you reach the loading area for the rides or the seating area for shows. For those that are not mainstreamed you will be directed by either signs or a Cast Member to an alternate entrance.
Just be aware that in a chair or ECV you will
not get any Front of The Line privileges.