Travelling with kids for extended drives in a motorhome is a different experiance than travelling in a car or truck with passengers seated in static positions.
Passengers in a motorhome can get up and walk around, use the bathroom, watch TV while stretched out on the couch, get something to eat or drink and the view from the larger windows helps as well. Kids enjoy being the navigator or co-pilot. Heck my kids normally go back to bed, on the rear bed after breakfast and sleep in for a few more hours like normal teenagers.
It helps alot if your spouse can drive a bit, even for an hour or two at a time.
Plan to average 50 mph. I, like others, have discovered it does not matter what you do, where you stop, road construction delays or how far you can get between gas stops it always works out to 50 MPH on average.
I have done long drives with kids in our motorhome. I recommend the five travel day each direction plan as well. You might get away with a Walmart stop for one or two nights in each direction but with kids you want to consider setting up in campgrounds more often then not. Gives the kids a chance to get out and run or roam, at the end of the day, in a non-parking lot situation. Our biggest issue with the kids is when we overnight in parking lots, they get bored and it is not really a place we want them out running around. Plus a campground gives you a chance to sit outside, maybe have a fire and put your feet up for awhile, something frowned on in the Wally World lot.
One other thing. Leave an extra day for the drive home. Stay 7 nights instead of 8 at YS. If you had a delay on the way home and you are against your time limit for days off it could cause issues at work. I highly recommend at least one full day at home before returning to work after a long trip. Kinda like scuba diving, you need to depresurize before you "come back to the surface"