Frankfurt to Bordeaux by car with kids

Looking at a suggested route on Google Maps I see it passes through Champagne and the Loire Valley. Champagne would be worth a stop (at least for the adults). And definitely the Loire to see the chateaus. I would think any child would be impressed by them. Or you could take an alternate route through Alsace, and then the Dordogne towards the end. Both would be great choices.

If you're going to head through Paris, then definitely a day or two in Paris. On the way there, the kids are old enough to stop in Verdun to appreciate world history, perhaps a day stop at Disney Paris.
If you head south, go through Strasbourg and a few wine route towns, or stay on the German side and stop at Europa Park (you'll be able to his most of Europe in one stop!). Head through Beaune, then some smaller towns on the way to Bordeaux.

The family might like Guedelon: http://www.guedelon.fr/en/