I agree with what someone else suggested--have your daughter get legally married at home and then have the 'ceremony' on island. I think the priest might be a problem, as many ministers of any religion will not marry someone that they do not do marital counselling for. As far as a place, I might suggest Dreams. They are on the beach, but the setting is very elegant and the party could be there and pretty much never touch actual sand, except walking to and from the car..