3 week trip - Colorado, Utah, Arizona

For three weeks, I would probably pick only one state. Colorado would probably be the coolest, or southern Utah (the north rim of the Grand Canyon is higher, cooler, and less crowded, and is close to Zion and Bryce).

Only you know your traveling habits but if you did a similar trip to Yellowstone in that timeframe then, yes, you can do it.

Keep in mind though that Utah and Arizona will be very HOT in the summer and some of Colorado can be, also.

I'd head to Arizona at the beginning of summer. There are some nice Indian ruins around Flagstaff (and you'll have very cool temps there), do a day trip to Sedona (too hot to stay there) and there are more ruins in that area around Cottonwood. Then do the Grand Canyon and stay IN the park for the best experience. Trailer Village is the place for full hookups. Mather or Desert View have no have hookups.

Then head for the Utah national parks - Zion, Bryce, Capitol Reef, Canyonlands, Arches. For Arches reserve a spot ahead for the Fiery Furnace ranger-led hike. The kids - and you - will love it. You'll be in a shaded canyon with fun walking. All hikes should be done early morning because of the heat. Take lots of water...get a waistpack for everyone to carry extra.

In Bryce do the Wall Street hike. It's amazing! Drive Hwy 12 to get to Capitol Reef - gorgeous.

Don't try to do these parks from one or two base camps. That just involves a lot of unnecessary driving and time. Stay IN the parks.

For Colorado, I'd concentrate on the SW corner - Pagosa Springs (nice soaks and a huge pool of hot spring water), Durango (instead of the costly train ride to Silverton - just stay in Silverton, (the best scenery you'll see on the whole trip) Montrose (Black Canyon Nat'l Park), Cortez for Mesa Verde National Park - take the ranger-led hike to the ruins - involves ladders and crawling through a tunnel - fun.

You'll all be tired after this vacation!

We just got home from a two month trip to the same states. One gem we found was Great Sand Dunes National Park and Preserve. Recommend you stay at the Alamosa Colorado KOA. It's a really nice RV park.

When you visit the dunes, rent a sand board and ride down some of the dunes. It's very safe, and loads of fun. You can also take your doggies onto the dunes as long as they are on a leash and you clean up after them.

While in Alamosa, visit the Colorado Gators reptile park. You can get discounted tickets at the KOA.