I already know that I want to particpate in several excursions while I am at CSS, and because I can't use my 500 resort credit for excursions I had to save up some extra money last minute. So I guess my question is which is cheaper, setting up a tour at the resort, or setting them up ahead of time? I was going to use Chukka Tours.
It's the same either way. If I were you, I'd wait until you arrive at the resort so you know the daily activity schedule. If you book now, there might be something happening at the resort that you won't know about and don't want to miss.
What I do is check out sites like tripadvisor to see what people say about tours and the various ways they book them. I would also do as Amy says in not booking ahead of time. Once there you may just decide that floating in the warm Caribbean waters with a drink in your hand is all you feel like doing on any given day. Or all of them for that matter! We find 4-5 things we may want to do and if we do 2 of them we are happy. Remember that you are already going to Dunns River Falls which is included. Take water shoes.