Those who can only travel 300-500 miles per day obviously need more time to cross the country.
That's not us.
Maybe you can cover more ground too? If a few of you drive the RV, you could drive just about non-stop. It will also depend upon how the entire group travels. We are fortunate that our two kids travel well and don't get frazzled. A road trip is nothing to them. We regularly make it back from Key West in 2.5 days, no sweat.
Our cross-country trip this past summer:
We left West Virginia on FRIDAY after work and pulled into Moab, UT in time to set up camp, take a swim, eat dinner in town and watch the sunset in Arches on MONDAY.
The better half drove a little in Kansas. Other than that, it was just me. I have been able to do that all my life. I guess I missed my calling and should have become a truck driver?
Once we got out "there" our pace slowed a little, I guess. Our plan was to jump around and hit the big ones: Arches, Canyonlands, Dead Horse Point SP, Capitol Reef, Bryce, Zion, Antelope Canyon, Monument Valley and the Grand Canyon on the way out.
After this leg, we went to San Clemente for my Nephew's wedding over the 4th of July weekend. We managed to take in two days at Disneyland while there for the wedding though? Hey, you can't go all the way out there and not do Disneyland, right?
Then we made a big circle (DW insisted the kids see Yellowstone?) (glad she did): Sequoia, Yosemite, San Fran (with Muir Woods nearby that has Redwood trees), Yellowstone, Mt. Rushmore and Badlands.
On the way home my 13-year-old daughter did say she couldn't wait to sleep in her nice big bed. That was the only grumpiness on the whole trip. Even our dog Ozzie was pleasant throughout. Not bad, huh?
When planning all these stops we told ourselves that it was not worth one person being miserable. We promised to pull the plug and hunker down in one spot if that happened. The kids were too excited to see the next spot. We kept moving. They stamped their passports at each NP and learned a lot in the visitor centers. Then we hiked or biked to see what sights we thought were most important. We rode our bikes around the Yosemite Valley trail. My 8-year old got a 6-speed bike for Christmas in preparation for rides like this. It worked. He kept up and left us in the dust at times too?? We ate lunch out of a back pack most days but slowed down for dinner just about each night.
My plan was to find CGs close to the parks but not travel up into them with the MH. We chose well-developed CGs to ensure easy in and out with level pads and full hookups. We weren't there to "camp". We were using the rig as our mobile hotel room. We towed the Jeep and used that to get into and out of the parks. We ate out a lot. I love to break out the camp stove and cook and have a fire, but we did not do that much on this trip. We had a reservation for each night once we got to Moab. We winged it on the trip out and back. We stayed in a Casino lot one night and hit a couple of rest areas too. That's the only way to make time on the crossings. We don't want to pull into CGs late when we will bother those who are relaxing.
Did we see it all? No way. Did we miss a bunch? You bet. But really, unless you take a whole year or two, you are going to miss more than you see anyway.
We were simply making the most of the one time we were able to do this. Most likely, we will not be able to go back with the kids. My wife can take thirty days from work no problem, but it was most likely a one shot deal for me. So, that was our one-shot cross-country adventure with the kids.
The DW and I did do a similar trip by car with a tent about twenty years ago. (another story with similar itinerary).
I will admit that our trip was fast paced. We knew that going in and took it on as a challenge. We did manage quite a few hikes and bike rides. We even went into Bryce Canyon on horseback (make reservations for trips like this).
So, can you do something similar in 3 to 4 weeks? Be honest about the entire group's desire to go fast paced and make that decision.
If you can have more trips like this in the future, I recommend breaking it up into areas and stay there longer. Maybe plan three years in a row or something like that.
Redwood NP is a hike up the West coast for instance. I would recommend a straight shot out to the coast and doing Redwood and the Northwest parks one year. Then, spend a trip on the Southwest. Maybe do a Rocky Mountain/Yellowstone/Black Hills trip one year.
Good Luck on your trip, whatever you decide!