Kinda tough. You can't just park it anywhere in the park, as that's illegal. You've got the tunnel mountain and two jack lake campgrounds. But neither are close to the river. Well tunnel is, if you want to repel down the hoodoos haha.
EDIT: just to clarify, you can't CAMP anywhere you want in the park, you can park the trailer during the day (but hopefully you can just detach the truck, it will make things a lot easier).