128 north of Moab along the river may be the prettiest stretch of road I've ever ridden. I've been through Yellowstone on a bike, IDK if you've been there lately, jammed with tourists and trailers, I wouldn't do it again myself.
Ironically I'll probably be at Yellowstone 4th of July weekend now. Ahhh life, how you like to throw money wrenches.
I looked into 5 in 5 concept for Utah, it looks great but has some very very short riding days. So I'll see what's along the way to extend the riding between stops... Unless you all want to go hiking instead of riding at the parks (I know I'd rather be riding).
Riding through the Parks and stopping for the sites is good, but some hiking is good. I say some ... meaning not to vigorous. I would like to take the full walk to Delicate Arch.
BTW: The last time I visited Zion they limited vehicles in the Canyon. They have shuttle buses and then you walk.