Yeah sounds like a mare.
I would drive only at night.
If you are happy to spend 5-6days on the road
Do it like this, this is what we do when we drive to skiing.
5pm feed kids.
6pm get in car, have sing along, isn't this jolly, la la la.
8pm kids asleep.
share driving with DH through the night,a nd sleep in between
8am, stop for breakfast somewhere : earlier if kids wake up.
9am drive until 10 - 10.30am
Stop somewhere fun, eg play ground, farm, etc
run around, play for a couple of hours, have lunch:
2pm Back in car for two more hours driving, one of you sleep.
4pm: stop for run around, play, and tea etc, wash too hopefully.
6-7pm back in car, drive all night again.
You get about 12 - 15 hours driving in a day, it works well. for one night, not done it for more..............