Its an Ecosafe system that you want - that's the plastic tank insert for an ammo can that has a toilet seat that attaches to the tank. the tank has a sealing top and then you close the ammo can over the internal tank, that gives you a second level of containment for your poop. They can be emptied at RV dump stations very easily using the 4" RV dump hose that's part of the system and neatly screws into the inner tank. You'll need to have a 8' section of garden hose with fittings on each end - that'll mate to an inlet in the plastic insert - turn on the hose and the tank gets flushed out. You don't need the bacteria for a 5-day trip - just sprinkle a little powdered bleach in there before closing up the groover each morning. There's minimal mess and smell involved with the whole setup. Here's the scoop on the pooper:
ECO-Safe Toilet System
Check with RiverRunners in Vernal UT, ( "Self-guided, full support river running and white water rafting adventures: safe shuttle services, full or partial support river trips available, and complete, delicious meals are prepared. Whitewater river trips include: Gate of Lodore, Lower Yampa
) they can rent you the system or you can just divide the cost of a new one among the group for about $10 each. I honestly can't figure out why some folks still insist on using an open, plain ammo can after using the ecosafe setup...
There's a RV dump station at Split Mountain where you can empty the groover. I'll be surprised if they allow a plain ammo can in Dinosaur as they probably got sick of cleaning up the dump station after folks getting crap all over the place dumping their ammo cans there. You can check the regs here: Dinosaur National Monument - Private River Rafting Information (U.S. National Park Service)
have a good trip!