Planning Yellowstone/Grand Canyon trip from VA

I would agree Rocky Mtn would probably be a bit boring after Yellowstone plus Flaming Gorge will be crowded in July. But to stay away from the crowds, you could consider leaving Yellowstone to the north and pick up Theodore Roosevelt NP in ND the continue to northern Minnesota and Wisconson. Temps would be nicer too.

Here is a thread on North Dakota and another one on Upper Michigan.