Some observations from one who often travels to many of the places you mention:
1. Although you say you don't want to make too many reservations, there are a couple of caveats. For one, you will be travelling over the July 4th holiday, along with every other RV'er out there! Camp spots can get very dicey that week w/o reservations. Also, many of the areas you mention are very popular all summer, esp. around Ouray, Durango, and the NP's.
2. Do note it will be very hot in much of the desert area. Your stop at Glen Canyon is an example. My guess is it will be well north of 100 degrees there in late June. Do you
really want to stay there that badly? Likewise, the Moab area will also be quite hot. The average high is right at 100 degrees, so if it's above average. . . :E Consider camping up in the LaSal's (NPS CG's) or reserving a spot at Dead Horse Point SP (higher in elevation than Moab but still hot -- there is elec. service up there to plug into for A/C). There is some sightseeing to be done by car, but it will be very hot during the daytime. Take lots of water and do the short hikes to the viewpoints in the middle of the day. Also, try to plan your hikes to take advantage of the shade of the canyon walls. For instance, the hike up Negro Bill Canyon is nicely shaded in the afternoon, hence "cooler". Zion will be hot, but you can play in the Virgin River right by the CG under the shade of the cottonwoods to cool off. Hike up the Narrows in the heat of the day. Figure out which side of the canyon will be in the shade to determine which trails to hike. The one thing nice about the desert is it
usually cools off nicely in the evening.
3. One night at the Great Sand Dunes is more than adequate. By mid July, most likely Medano Creek will no longer be flowing. The creek flowing in front of the dunes is one place the kids love to play, but once it is dry, climbing the dunes gets pretty tiring after a few hours of heat. The kids probably get a lot of playing in the sand closer to home anyway.
4. IMHO, one night at Colorado Springs would do me. For some of the days you save at CO. Springs and Great Sand Dunes, I'd head to the Salida/Buena Vista area for a few days. Sooooo much there that the boys will love. Ghost towns, river rafting, easy 4x4 trails (hard one's too!), fishing, and CG's high enough up in elevation to be cool in the evenings.
5. As previously mentioned, Bonito CG is a great central base camp to visit Sunset Crater, Wupatki, and Walnut Canyon NM's. You have three nights designated for all three, so I'd just pick the one CG for all three nights and avoid the move.
6. For Mesa Verde, you might consider a couple of nights at the NPS CG on the mesa. Higher and quite a bit cooler up there. FHU available. This puts you closer to the ruins. Get your tour tickets at the Visitors Center before you head up. Also, there are a great many ruins on top of the mesa plus viewpoints, so it's not just about touring the cliff dwellings.
I answered a somewhat similar question to yours about a year ago.
Click here to check out that response. There are some good links there for you to check out, such as the Durango Silverton train, info on 4x4 trails around Ouray and info on the Salida/Buena Vista area.
