We also went to Dolphin Discovery in Cozumel. We all (myself, dh and dd who was 8 yrs old) enjoyed it. It is at a National Park and there is a lot to do there after you are done with the dolphins(sea lion show, pool, beach, and more, all included in the price). If you do a search on here you will see several threads on it, all positive. You have a slighter higher chance of excursions getting cancelled at Grand Cayman's than you do at some of the other ports, because if the seas are rough they sometimes can't tender. Our excursion(stingrays) was cancelled the night before when we went to GC. The weather was nice sunny skies, however the seas were rough and the operator notified Disney the night before that they were cancelling the excursion. We had booked through Disney though so we were reimbursed. Even the beach excursions were cancelled, we were able to tender, but people were scrambling to find excursions. I was glad we had done the dolphins in Cozumel, I would have been disappointed if we had it cancelled in GC. Of course there's a chance any port could be missed due to weather or other reasons. Luckily we were able to do the stingrays in CC.