Great choice with the ship! My friend and I took the same cruise last November and loved it. First, there is really good information at carnival.com/shore excursions, if you happened to not already find that.
In Ocho Rios, we did the Dolphin Cove & Dunns River Falls excursion through the ship's service. Climbing Dunns River Falls was an experience of a lifetime that we wouldn't want to have missed. Our tour included visiting Dolphin Cove which involved watching to dolphins from afar, taking their little jungle tour where we were introduced to toucans, lizards, boa snakes, their coffee and then shopping. There was food available to purchase there. Just visiting Dolphin Cove wasn't worth the money of the tour to my friend and I. If you're interested in encountering dolphins, spend the extra $ to do the touch or swim tour. Our tour dropped us off at a smalls shopping center where we found great buys on souvenirs as we shopped around without buying at the first place. The ship's shopping talk had given out coupons for a free shot at Margaritaville which we had a great time out, bought souvenirs, etc.
We did encounter several individuals trying to sell us drugs or marijuana. Just warning ya so you're not surprised. We received no harassment when we simply said "no thanks" and kept walking minding our own business.
Another piece of advice, I wouldn't wait until the last minute to try and hail a cab back to the ship. The cabs get very busy close to debarkation time.
Hope this is helpful.
