I am handicapped and use a power chair. I borrowed manual chair from Guest Services for Grand Cayman. The big tenders have very few stairs, I am able to transfer with assistance, 3 very strong very patient men made sure I was ok. I asked what would happen if unable to walk, they said seas permitting they would carry the occupant and chair onto the tender.
I would recommend calling guest services Grand Cayman morning to see which part of the ship (aft or forward) the large tender is using. Grand Cayman is pretty easy in a chair. The 2 story mall place even has a handicapped bathroom. Where Harley Davidson store is, on 2nd floor (use elevator).
Sherry