Recommendations for Private Snorkeling Excursion (party of 12)

[Castillo Mom]

We're considering doing a private excursion (not through DCL) when we're in St. Thomas/St.John. Any recommendations for a party of 12? We're looking for a catamaran or powerboat/yacht type experience that serves a nice lunch and has a dingy that can take us out onto the beach. Anyone ever done this and how was your experience?