Are you staying with points (your own or renting points from a DVC member)?
If yes, then Member Services takes care of any special needs, like needing a first floor or elevator room for medical reasons.
If you are making a cash reservation thru Disney, then you can ask for Special Reservations.
I would request ground floor floor or in a building with an elevator for medical reasons (it is important that they list it as medical reasons). That would be your first request. The second would be close to HH.
They DO block out and preassign the requests for the rooms that are wheelchair accessible (like the rooms with roll in showers). The "medical reasons" (like for first floor, but not a handicapped room) requests are not guaranteed, but you are pretty much always going to get a request for first floor or elevator. If you ask for a specific building or
only list the elevator buildings, you are not likley to get what you ask for.
There are elevators in buildings 62, 63 and 64. I would not specifically request those buildings though because they are in high demand (they fit if someone asks for an elevator, close to a pool, close to a bus stop, close to HH).
Here's a
link the DIS site information page about OKW. The resort is very nice and eassy to get around with someone who is using a wheelchair. The pool at HH has been recently renovated with a slide added. The pool at Old Turtle Pond is more than a quiet pool. It doesn't have a slide, but does have a hot tub and snack bar.
Here's a
link to the OKW map from the DIS site. buildings 23 -26 are not as far from the pool as they look. True, you have to walk along Peninsular Road (there is a sidewalk); you can't just cut across because of the water. But, you are closer to the back side of HH, which is where the pool is. The tan line on the map that goes between the pool and HH is a walkway. It connects up to the sidewalk by Peninsular Road so you can go directly to the pool area from there from buildings 23-26 instead of having to go to the front of HH. (This might not make sense now, but it will when you are there).