Yeah I guess I needed to clarify some of this a little bit more.

It's looking like there would be 5 of us in the vehicle, plus our stuff and some camping equipment because we would rather camp and not stay in a hotel every night.

We really want to focus more on what there is to do in each of those cities because we'd spend a couple (3?) days in each place, but we want to see those places that I mentioned and probably not too many more.

We were thinking maybe around 14-16 days?

We have people to stay with in Seattle, as well as in northern California and Colorado which will keep cost down on housing. And we plan to get most of our food from the grocery, with the occasional restaurant meal.
I guess I should ask for a guess at what you think the cost will be too.

I think we are going to try a short trip earlier in the summer as well to make sure we understand what we're going into, because it's a pretty long trip.