We have been here and done that a few times. Some of our party went to Dunn's River Falls on a private excursion booked on arrival. They had an excellent time but said that it was crowded and the sales folks were pushy.
We find this port to be stressful no matter which excursions we book. There are always people trying to sell you things and they are very pushy and often use uncomfortable tactics, such as complimenting my youngest child on her shoes and then telling her that if her mother would buy something they could buy their little girl nice shoes too. Very hard to explain to a 4 year old.
On previous trips we have gone to the beach which has been beautiful but we never really feel safe in Jamaica.
Stingray City and Snorkel. We've done it so many times but it is so much fun to see these creatures out in nature. As a family we love to snorkel with the fish and to see them up close and feed them. Truly great times with the kids.
The port is a little more expensive than many of the others.