I did a similar trip with my son in 2018, in early May after he finished his semester. We flew in and out of Phoenix. The big difference is that we camped in the Grand Canyon park. Was wonderful, even though the weather was still cool. We brought a tent, but I rented a car that was big enough to sleep in if the weather was truly awful. I got up to see the sun rise over the canyon, which was an incredible experience. We hiked into the Canyon to the 3-mile rest spot.
We then went to Flagstaff for one night, staying in a KOA camp cabin, luckily because the weather was terrible and we actually went to the movies and then found a rock gym. On to Sedona where we stayed in a hotel, because the campgrounds were not open yet although turns out they might have been. Great hiking plus good restaurants and interesting shops.
All in all, a great trip. If you can, stay at the Grand Canyon. Well worth it.
Phoenix is a great trip as well.