If you're not going horseback riding, the tour of Prosepct Plantation and Dunn's River Falls is really worthwhile. The plantation actually occupies most of a mountain, and there's quite a science to the way that they plant various crops according to altitude. They really do grow an impressive array of crops that would be the envy of most farmers here in the States!
As to Dunn's River Falls, be sure to plan to climb. All you need are a bathing suit, a towel,and a pair of Surfwalkers (available at most any sporting goods store). The climb is not exceptionally difficult. In fact, a woman who was 99 years old did it just before my last visit. The falls are well shaded, so there's no problem with sunburn, and the river is very refreshing.
BTW, if you do the Prospect Plantation tour, just wear your street clothes over your swimsuit. You can leave your street clothes and valuables in the van while you do the climb. The driver will protect them for you.