Take us89 north and make the loop via Sunset Crater Volcano, Painted Desert and Wupatki NMs. Then drive to Cameron for the Trading Post. Enter GCNP by its east entrance. First stop inside the NP will be Desert View. On the way between Cameron and Desert View you can make a stop at the Little Colorado overlook (small fee). On the way back you can take 64/180 back to Flagstaff or drive via Williams (cute R66 town) and I40 east.