Once you pay the nightly rate for tent camping, is there and additional charge for the pool and the other activities?

No once you pass the gate into the park you can do everything. Equipment rental for some things is not included like tubes to float the river but you can bring your own. They also have a craft room that you need to pay if you want to do the crafts, it is optional. They also have water balloons for the water fight night during the summer, those cost, they are up at the Check in place. Or you can bring your own. The pools (2) are free. And the river is free to use.

I think that's all included.