Depends on the weather, which hasn't been promising so far this winter as you should know. Down on the southern end of this trip you should be OK. Not much in southern Idaho unless you like to climb rocks, City of Rocks is south of the interstate.
We really need more info from you:
Do you plan to do the SW Utah parks?
What are you interested in? Hiking or finding urban areas to visit.
The North Rim of Grand Canyon will still be closed.
What about the AZ parks south of GCNP?
What are you going to camp in, what type of RV
What are you driving?
