Trip Planning or Dreaming?

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We're starting to talk about taking a big trip to see the West before the kids get too surly (as teenagers) and here's a preliminary route. I'd like to stay a couple days at the major stops and not feel rushed in between. Please weigh in with any suggestions of sites to see or places to visit.

Here are the major stopping spots:

1. Start at the Gateway to the West (St. Louis Arch) and roughly follow Lewis and Clark's route to the north.
2. Visit family in Omaha, Nebraska
3. Yellowstone National Park, WY - need to spend a couple days here
4. Mt. Rainier National Park, WA
5. Visit family in Bakersfield, CA
6. Grand Canyon North Rim Lodge, Arizona
7. Visit friends in Colorado Springs, Colorado

Possible minor stops along the way:

1. Arches National Park, Utah
2. The Badlands, South Dakota
3. Laura Wilder's homes in Kansas and Missouri
   
4. Seattle's Space Needle

Any other MUST SEE places? This is still just talk and money hasn't entered the conversation yet so it's still fun =)