As far as I remember seeing they did not have wheelchairs on board for use, but I could be wrong here. They do have a "Sand" wheelchair for use on Castaway . I rented a power scooter from an off site place and used it on board. Yes you can get off the ship at most ports, however I am not sure about all of the western and eastern ports. Most islands are not up to ada due to being different countries they dont have to be. A lot of shops have steps up to the doors, and no ramps, stuff like that. I normally stay on board regardless, but if I do venture off I find the islands difficult.
Aimee