If you're renting an RV, do we assume you don't have transportation other than the RV? If so, this is a BIG factor in your enjoyment of this adventure. Keep in mind, it's not easy to maneuver an RV to go get a pizza or around some national park roads.
Regardless, it's a bit ambitious depending on how much you'd like to do at each location. I understand vacation limitations, but consider eliminating one of your parks just to allow more time for fun in the others. If you like to hike, there are many hikes for early teens - or just ask at the park visitor centers.
At Grand Canyon, consider onsite Mather Campground - close to the bus system so you may not need a car. (no hookups, but the nearby Trailer Village does - also in the park, not sure if it's within walking distance to the park busses).
Zion National Park - Watchman Campground, next door to the visitor center where you catch the bus up the scenic route not open to traffic. But book soon, they'll be all sold out (see my blog post
"Best Site in Watchman Campground, Zion National Park" .
We also really enjoyed staying at Fruita Campground in Capitol Reef National Park. The geology ranger led hike was very interesting depending on what your kids are interested in. You should check, but maybe the orchards would be bearing fruit so you could pick your own (we were there in May - no fruit). Also there are amazing hot fresh baked cinnamon rolls and fruit pies at Gifford House right by the campground. Here's a blog post about our favorites at Capitol Reef NP:
Top 10 Experiences at Capitol Reef National Park Whatever you decide, ENJOY! What a great trip for the kids (and you!).
Cheers! Jan & David
Just returned from our First "Snowbird" Winter ... 25,000 miles, 26 states, 23 National Parks ... and counting....
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