We just got back from cruising on the Destiny (Sept 27th-Oct 2nd) and we did the mini-boat tour and Dunn's river falls. The miniboat tour was a blast, my husband and I each had our own boat with a guide. We were racing each other through the waves while our guides would show us which way to go (we were driving the boats ourselves). Every now and then they would have us slow down so that they could point out various landmarks and they were very knowledgable and answered many of our questions. We took the boats all the way to the base of Dunn's river falls.
The Falls were so much fun. The rocks are not slippery at all and while it is quite a workout (we were both sore the next day LOL!) it is very well organized. There are always several guides helping out those that need a hand climbing. Neither my husband nor I are in perfect shape but we made it up without any incident. Every now and then we would stop and swim in the pools of water. Feeling the water cascading over and around you is so liberating. I must say that even though my husband and I are both a little out of shape we managed to do the climb without any problems. I would highly recommend this excursion.