I am cruising the same ship/western itinerary in May. I have found www.wildernessatvtours.com/atvtours.htm
to go 4 wheelin in Ocho Rios. It will also take you to Dunn's River and seems like a fun excursion for the price. For research try tripadvisor.com and just type in each destination and you'll see the top rated choices for things to do. I have had great success using tripadvisor in all vacation planning. You can also try cruisecritic.com, they have alot of boards on there. Hope this helps.
Enjoy the Libery. I can't wait to go.