Is our summer trip out West too ambitious?

Tim, renting a car is a good idea so no need to stay at Fishing Bridge for more than one night. Four miles north of W Yellowstone is Baker's Hole USFS CG which is much cheaper... enough to pay the car rental and some of the sites have electric. Double you house battery bank, install an inverter, and you will not even have to run your generator all that much as it's cool enough to not need AC in WY. Crank the generator for the Micro and to recharge your batteries during supper.
Getting around the Teton's in your C will not be a problem. Do not bump the trip up a little, bump it up a LOT.