Is a HA room necessary, if so, make sure you put that on your reservation.
Obviously once in the parks there will be a lot of pushing you around, but once there you could rent an
ECV albeit an added expense or you could rent from one of the many off site rental companies, they will deliver it to the resort, and then you will be able to use it around the resort or to get over to the Boardwalk.
The buses are equipped to handle an ECV or wheelchair.
I have used EVCs on occasion, I too have difficulty walking long distances at times, and they are great. They are also good for carrying around any refreshments you might bring to the parks in a cooler or backpack. Something to consider.
Have a great time at BCV, it's my favorite place to be, going there in 2 weeks.