The problem with the Grand Canyon is picking a rim. I suggest the north rim due to the general lack of annoying tourists, even though it’s a longer drive. Then again, I’m a bad person to ask about such things, mostly because of my dislike of the way many tourists interact with the national parks.
Also, it’s my experience that Easterners don’t have a good grasp of distances. You can do in a couple of hours driving what can take three or four in the east, depending on congestion and relative speed limits. But things are very far apart, so even if you’re doing 80 mph, it’s still 4 hours from Vegas to Flagstaff. It’s 8 hours from Denver to Jackson, WY or 5 hours from Salt Lake to Jackson. And there’s a whole lot of nothing in the middle. I mean, there will be things, but don’t count on being able to find gas right away, for instance. The closest analog I ever found on an interstate back east was I-88 in New York.
Can I suggest Rocky Mountain? Estes Park is expensive to stay in, but it’s reasonably close. You can stay in Denver if you’re willing to drive 90 minutes each way. Plenty of times I’ve seen people pulling off the road to gawk at elk. Plus, the alpine tundra in the spring is pretty.
Arches NP is full of excellent little and medium size hikes. Perfect for the spring. Totally unique scenery. Moab is a good base for exploring. If you or your sons are into mountain biking there is all kinds near Moab from dirt roads to rollercoastering over sandstone formations.
The best way to experience the Grand Canyon IMO is by the river. I don’t know how long ahead of time you need to plan, but it’s really the most magical. You get the excitement of white water rafting, lots of little hikes to watery and green places. Watch the canyon walls rise up as you go through. Sure it’s camping but it’s pretty deluxe camping.
Might i recommend one that is probably the furthest for you while staying in the Lower 48? Olympic National Park in Washington State. Here, it’s all about diversity: You got mountains, glaciers, rain forests, alpine meadows, waterfalls, hot springs and miles of wild Pacific Ocean coastline. Wildlife in elk, deer, bear, mountain goats and smaller mammals. This is a sampling of what it looks like.
Fly to Seattle, rent a car, take the ferry across Puget Sound and then several days making a loop around the peninsula. The highway circumnavigates the park providing jump-off points into the park. Plenty of motel and lodges. Places not to miss (IMO) are: Sol Duc Hotsprings, Hurricane Ridge (probably the best view of the interior of the park without hiking into the backcountry), Hoh Rain Forest and Kalaloch Beach. Everything is pretty accessible, lots of day hikes, self guided nature tours and the like.
I concur with the suggestions about the Southwest. Southern Utah is a national treasure, as are many of the surrounding areas that contain such places as Grand Canyon and Antelope Canyon in Arizona, and Mesa Verde in Colorado.
Last year we spent 3 weeks driving cross-country (west to east) and hit Zion, Bryce Canyon, Grand Teton and Yellowstone along the way. My kids were 9 and 11 at the time.
I agree with the others that the Southern Utah parks are great but Yellowstone is better for wildlife. I wasn’t as impressed with Grand Teton in general, although we did get a couple of moose sightings.
We loved the geological features of Yellowstone: the geysers, fumaroles, hot springs, etc. Zion was crowded (we were there in August) but the Narrows were neat and my kids had a great time swimming in the river. But my favorite part of Zion was not in the valley, it was the Checkerboard Mesaon the way to Bryce Canyon. There’s all these totally cool rock formations. We just pulled off the side of the road and wandered around and it was fantastic.
If you end up in southwestern Utah, Valley of Fire State Park in NV is not too far and is a hidden gem IMHO.
One tip I have is always bring chocolate or some other form of candy on a hike. My kids complained a lot about the hiking (which was NOT strenuous!) but doling out small pieces of chocolate at regular intervals helped immensely. Later we discovered Pocky and that is now our go-to snack to bring on hikes.
Good point, I forgot about this. The most amazing night sky I have ever seen in my life was from 12,000 feet on Mount Shasta. No moon, no man-made light pollution, and a significant portion of the atmosphere was below me instead of above me. This was upon waking in the middle of the night, so I had complete night vision, but you should be able to achieve pretty good night vision within 5-10 minutes of extinguishing all nearby sources of light.
Similar viewing conditions (altitude, light pollution) should be possible at these parks (you’ll want to drive to an isolated scenic overlook).
Banff and other canadian parks will be mobbed next year as they have free entrance in 2017 and are a key component of Canada’s 150th celebration.
Next year is an excellent year for it too. Canada will be 150 yrs old and we’re celebrating with free admission for the entire year to all National parks.
See what happens when I post without reading to the end. Leaving as I disagree with Disheavel’s conclusion 
Keep in mind that late spring and early summer there will still be considerable snow in the higher elevations of Yosemite, Yellowstone/Tetons, and Glacier. Tioga Pass in Yosemite generally doesn’t open until mid-May. And summer months in the desert southwest can be brutal.
7-10 days…hmmm…I think it all depends on how much driving you want to do. You could certainly to a big loop out of Denver or Salt Lake City and see multiple parks but not have a lot of time for any one place. Or you could just as easily spend a week just in Yellowstone/Grand Tetons or base yourself in Moab to see Arches/Canyonlands for the same amount of time.
One thing I’ll add is the National Park Passport. I was just at Sandstone NP in April and picked one up (and I’m an adult). I can see kids really getting into collecting the stamps.
Thanks for all the great information! I’ve decided to do the Grand Canyon/Utah Canyons trip. We have family in Las Vegas so it makes sense to fly in there, see them, and then rent a car and head out. Our Spring Break is the week of April 10. Is that time of year okay for the canyons?
Bump to hear information about the weather in early April for the Utah/GC area?
A couple years ago we stayed in Zion in early April and it was perfect camping weather. We originally had planned to camp at Bryce but it usually is on the chilly side there in early April (we did do a day trip there and it was sweater weather in the daytime: there was still snow on the ground in places and seemed like it got cold at night.)
We had planned on doing a day trip to the North Rim, but, at least that year, the roads to the North Rim were still closed due to snow, and we felt that a day trip to the South Rim would take too long from Zion.
Check out the web sites for the various parks you’re planning to go to - in Grand Canyon, average April temperatures are 32-60° (low-high) on the South Rim, 29-53 on the North Rim, and 56-82 in the canyon itself. Zion and Bryce will have similar information available. In general, Bryce Canyon will be similar to the Grand Canyon rims and Zion will be more like the central canyon.
ETA: you’ll likely be limited to the South Rim of the Grand Canyon then - the North Rim visitor facilities don’t open until mid-May. Roads to the North Rim may or may not be open if you want to rough it, but I wouldn’t count on it.
Sounds like Spring Break might not be optimal time. School lets out around June 9, so maybe that would be a better option.
We have our children do the Junior Ranger program for each national park we visit. Have you considered those?
No, I haven’t even started looking at the parks yet, but I will check it out, thanks.