To close this thread out, at least as far the info for our trip goes, our drive took us well into the evening on the way through. We pulled into Spokane well after 10 pm. I did give Riverside State Park campground a drive through, but it was pretty full and my wife and I were not feeling comfortable with searching for an unoccupied spot and setting up in the dark. So we went back to Cabelas and that worked great. While she was at first skeptical on parking lot camping, she said afterwards that it was very convenient and worked out great. We planned on Cabelas for the return trip and it was again very convenient. That morning we headed in the store and spent gobs of money, just like they hoped we would!
Thanks everyone for their suggestions.
