I wouldn't do that tour from CSS. That is a better tour for when you are in Negril.
If you want to do a river tour, then Dunn River's Falls is included in the price of your stay. There is also a fun option of mountain biking. You are transferred up the hill and then ride down. Not tough at all. The hotel will also have other excursion options that they can help you with. I'm not sure why on the welcome email they gave you information about a Negril tour. Musta been a 'woops'.
The tour buses are fine for leaving the camera on. The buses stay with you on your entire trip and when you are not in the bus they lock them.
Juliann & Jeff
Jamaica Soon Come