We did not do any organized excursions on our 6-22 western Magic, and did not feel like we missed anything. We like to make our own excursions, both to save $$, but especially to go at our own timetable, and depending where we are, to go off the beaten path. We are myself, dh, and ds's 12-12-8
On Cayman we took a cab to 7mile beach (4$ each I think) and snorkeled using our own equipment. We went to the Marriott and ended up walking three resorts toward the ship. Based on where my parents went, I would recommend the Holiday Inn for restroom and food facilities. The fish were plentiful with a wide assortment. After a couple of hours we went back to the ship (tendering was very quick and easy) to drop the gear and rinse off and then DH and I went ashore to do a little shopping near the tender pier.