Roadtrip advice from Ohio to Seattle?

My wife and I are planning to fly to Ohio in May '05 to pick up a new car and drive home to Seattle. We've always dreamed of doing a cross-country road trip but are unsure which route to take.

We'd like to stick to the 2 lane highways as much as possible, but cannot spend any more than 7-8 days on the road...any advice?

I was looking at either taking US-2 through North Idaho, Glacier Nat'l Park, N Dakota, Minnesota and Illionois or US-20 through Yellowstone, Mt. Rushmore, Badlands, Iowa, Nebraska, and Illinois.

Has anyone done either/both of these trips? What is your recommendation?

Also, any advice on where to stop/stay and how much time to budget would be appreciated.

Thanks,
Chris

Both would be nice trips. My preference would definitely be Badlands / Yellowstone route.

No time to email further details right now - but to give you an idea of time - Yellowstone / Grand Teton national parks will need 3-4 days itself.

Note: Already pretty late to make reservations in the Yellowstone area for May '05. Better start looking!