I have a suggestion for the drive from Phoenix to Flagstaff. Stop in Sedona on the way up, but once in Sedona, take the Oak Creek Canyon scenic drive on the 89A (instead of taking the I-17). You can stop at Slide Rock State Park on the way up as well, although I'm sure it will be busy. Once you've made it out of the canyon, there is the Oak Creek Vista, just off the 89A to the right, that has some nice views.