Thanks to all who have made suggestions. Very helpful.
We are a large group and the cruise line has accommodated us with a place to worship on the ship, and they would tender us off as a group, and provide buses to get where ever we need to get on Santorini (it would be a custom shore excursion - $$$$ but we'd be happy to pay).
The question is, "Where are we going?" There are some wedding venues we could rent but I haven't found one large enough for our group (100+ and growing). Still searching. Just need a quiet and scenic place. Was kinda hoping that if we got somewhere first thing in the morning we could rent out that place for the morning before things really got going as more passengers come ashore.
Again, we could worship on the ship and then everyone head to Santorini on their own for a day of sightseeing. But if we could be together in God's creation for worship ... that would be very special. Thanks!