I think your dad could get on and off the fairy very easily but there is quite a bit of walking to get from one end of the island where the ferry boat pulls in to the beach on the other end. Most of it is above-ground wooden walkways and they are pretty level. Maybe even a wheelchair would help. I don't know if they provide them on the island
He shouldn't have too much trouble getting on the ferry with some help. Once on the island it's fairly level with a boardwalk part way to the beach.
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