My family is planning a trip to the Grand Canyon this summer from Seattle. They are a bunch of nature-fanatic, road-tripping-city-slickers, who-need-to-get-out-of-the-city-to-keep-sanity type of people. They have asked me to find out if there is/are particular routes from Seattle to GC that are scenic and which will expose them to a lot of the natural beauty of the the great U.S. of A. They're not too crazy about driving on major highways nowadays. They just want alternate and/or least known routes. Any suggestions?