Then in that case I guess I don't have much to offer but support.
but:
1 - Ensure to offer easy outs or girly options, always creates a built in insurance policy, River Runs Through it had multiple "outs" for most levels of riders.
2 - make sure there is a disclaimer poster (I am sure you remember river runs through it, you may not remember the signs at every entrance, with warnings and very clear displays of the type of trail, heck even a disclaimer of trail protection for weather etc)

I don't know what american laws would be like but that in and of itself is a bit of protection against the evil lawyers