I would pick a resort which reduces the need for bus transportation. CBR, POP AoA and Riviera offer skyliner access to 2 parks. The hotels around crescent lake, including Swan, Dolphin and Reserve offer boat service to 2 parks. You can also
scooter walk to 3 parks. WL offers boat service to MK. Monorail resorts offer monorail service to MK and EPCOT.
I don't think you can easily rent a van. Are you and your husband physically able to dissassemble a scooter and put the pieces in the trunk? The heaviest piece might weigh 40 lbs.
Skip the rental car. Mears accessible vans are much more reasonable then Minnie Vans.
What resorts are you considering?