If you decide on Stingray City, and I would definitely do that, I'd suggest booking through a company other than using the ship's excursion desk. We used Captain Marvin's and were extremely satisfied. Cost was much lower than ship and much smaller group. Do a seacrh on stingray city and you will find lots of information.
Grand Cayman: I did the Turtle Farm/Hell/Stingray Island and had a wonderful time. One thing that would have been nice to know before hand was to take your regular camera along with a h2o camera. I was afraid mine would get wet so I left it behind. Have a great cruise.
I agree with slouman and Penny. Stingray city is a must! We do that every time we're in Grand Cayman. Here is a picture of my wife swimming with a stingray. CLICK HERE
Did Stingray City in Grand Cayman. Wow! What an experience! Also, Dunn's River Falls in Ocho Rio's is great. Although, offered some drugs at the top. Just say no and walk away. I would still recommend to anyone going to Ocho Rio's. Also, did Turtle farm/Hell as well. It was interesting.