I personally was extremely moved by Oradour-sur-Glane and found it one of my favorite experiences in France. However I agree with the previous poster that it might be not understood and therefore somewhat boring for younger children. Maybe older children, those over 12 or so, who have learned about the history of WWII might find it a good learning experience.
With that being said, I don't think you'll have much time to make any sightseeing stops on that route, especially if you're driving out of your way to do it. That's a long drive and with kids you will definitely need to make rest stops, lunch, etc, not to mention that It could go even longer than 9 hours if you hit traffic, bad road conditions, or an accident that backs up traffic.