I would add Meteor Crater to one of the stops along the way. It is an interesting experience that cannot be appreciated with any film or pictures. It is just amazing that such a small meteor made such a large crater.
There is a great campground right along the highway at the junction that leads to the crater. The rates were very reasonable when we stayed there a few years ago.
And if you do make that stop, you MUST drive over to Winslow and have dinner at the Turquoise Room in the La Posada Hotel. It is a remarkable restaurant. (Why there is a restaurant of this quality in such an isolated area, is a mystery to me.) When you drive there you will feel like this is the worst advice you have ever had. The part of town where the La Posada is located is in serious need of renovation. But, once inside the hotel the world changes and you will realize you have discovered a really remarkable place. You will enjoy one of the best meals you have ever had.