Sounds WONDERFUL!! Back when our kids were going into 2nd, 4th and 6th grades (13 years ago!), my husband lost his job at the beginning of summer. We took a month long road trip and spent a lot of time in Arizona and Utah.
The kids' favorite place by far was Arches National Park. Something about those soft (to the touch) stone arches. Great for climbing around on...kids can really get in touch with the whole experience there...beauty, climbing, geologic history.
We did Monument Valley and did not go to Canyon de Chelly....a monumental oversight! Please don't miss either one!
Sedona is amazing! I believe we drove down from Flagstaff...the smell of Pine trees not to be outdone, going down that hill! Oak Creek is famous for its slide rocks state park
http://www.americansouthwest.net/arizona/sedona/slide_rocks.html
Unfortunately, we didn't know about it until after the trip. Your boys would LOVE THIS PLACE! We stayed in a gorgeous place up above Sedona....let me know if you are going to stay there...my husband will remember the name of the place.
We love Native American culture. We planned our trip around a lot of Trading Posts. I'll have to quiz my husband as to where. Hubbard Trading Post coming to mind right now. (these might be more in New Mexico)
We only had two days in Grand Canyon and had to stay in Page -- a 2+ hour drive!! (well, we didn't know he was going to lose his job! try to get any reservations 2 weeks ahead of time when it's already June!!) It is more amazing than you can imagine....any part of it!!
I wouldn't miss Yellowstone if you can help it. It's very family friendly (albeit ridiculously crowded). You think it's passe to see Old Faithful, but then you get there (after passing buffalo and moose, etc.) and there it is...really....! Just going into the lodges at Yellowstone is a treat. They are magnificent timber towers! also many steaming, acidic, bubbling craters in the ground at different locations....very science-y and otherworldly. So many animals, too.
We went to the Petrified Forest. It was okay, just a bunch of ancient logs on the ground. Not terribly kid tantalizing. Cool from the geologic history aspect, but I don't know if I'd make any special trip to it again.
Saguaro Natl. Park is amazing, but it's kind of just a bunch of cactus! There's a GREAT dude ranch (okay....husband and I went one summer for a week by ourselves) called Tanque Verde Ranch. Very well run and abutts the Saguaro Natl. Park. Wonderful naturalist talks and horseback riding. The Sonoran Desert Museum is close by and is phenomenal and very unique. In Tucson area.
We LOVED Mesa Verde. It is in COlorado, but very close to Utah. Fun to walk in and out of the dwelling. You really get in touch with it...they let you walk through with the guide and it's very informative and just the right timing for school age kids.
My son went to Zion while in college (in LA) one summer and truly loved it.
My father worked for the National Park service for many years and spoke quite lovingly about Zion. We'll get there some day!
There are all kinds of things to do on Lake Powell. It is quite amazing.
Glad you are planning way ahead of time. We didn't have the advantage of the internet 13 years ago.....you can do a lot of looking and the photos and descriptions tell a good lot about these destinations.
Hope I didn't go on too much. We had the most magnificent family trip. The biggest and best one we ever had together. You will be carving out a very special memory for your family. Good choices!!
Marguerite