I am planning on a similar trip in July from Cleveland to Grand Canyon via RT 66, when possible. I am interested in hearing about what you saw and suggested places to stop along the way. Since you will be going through St Louis, after about 4 hours of road time, you may want to stop at the Arch. If you want to take more time, there is a place called the Butterfly House which is FASCINATING...if is full of all kinds of butterflies!