We drive to South of France every year. we do it in one day, but that is because we are tight!
There are loads of cheap motels in France and we have had very good experience with them. Family rooms, clean and basic, chared showers and basic breakfast.
Places like Formula One, Campanile,
...and now the names of the other chains have gone right out of my head!
Every town has one or two.
be warned, it can be difficult to book a baby in, friend recently had this problem, you can't book them in but you can't have them in the room either or something. If you have an under 2 I can ask her what the deal was.
We drive down to near Toulouse, and from door to door including ferry and stops is about 15 hours. we are rigorous about stops, every 2.5 hours, snack, toilet and run around, we used to make kids run and touch 20 trees, or do races etc.
Dvd player, audio CDs, and air conditioning all essential.
We take a cool box with breakfast, lunch and snacks and then stop for a meal for dinner.