Tell him he can stay shore-based in the BVI while the rest of the crew enjoys St. John. Drop him at Scrub and tell him you’ll be back in a few days. Or, I suppose if it really becomes a sticking point everyone who wants to do St. John could take the ferry over for the day while the stick-in-the mud sits on the boat at Jost alone - though that doesn’t seem very fair to everyone else. Who’s the acting captain of the boat?