To add a bit more, we are bringing the whole family (me, wife, 3 kids (age 17, 15, 10). And we will be renting an RV. We did a similar trip years earlier when the kids were younger, and our route went across Nevada to Salt Lake City, then up to West Yellowstone, Glacier, back down to Boise, and back home. There were times when we hustled a bit to get to a destination, but it was more about the journey and seeing things along the way. That's what we want to do this time, just hit a little different area (if at a different time of year, we would likely hit the more scenic parts of Utah and the southwest, including Grand Canyon, but not during the summer heat).
Some great suggestions so far. If we do get into the Seattle area, I might like to see some of the stuff west of Seattle across the water, like Gig Harbor. But not sure. Although we won't shy away from cities, the goal is to see things more off the beaten path. We wanted to come up into Canada and possibly drive up to Whistler, but with the border close right now, that is not an option.
Anyhow, keep the suggestions coming!