We do this at a MUCH smaller scale being popup campers. Onboard fresh is 20 gallon. We have a 7 gallon blue Aquatainer and a 3 gallon Reliance collapsible. I bungee them both to a folding airport luggage cart and wheel the whole assembly to a spigot and back. Even 7 gallons is no fun to lift and dump into the fill, so we have a little Dcell 6v pump that will transfer the 7 into the tank in a couple minutes. The bubble is the picnic table water.
Our family of 5 can go about 4 days before needing a second refill trip.
Ain't much opportunity for boondocking in my neck of the woods, so it works fine in campgrounds.