If you love small, picturesque towns, then you will enjoy visiting historic Colmar. The town also has some wonderful museums such as the the home of Frédéric Auguste Bartholdi (sculptor of the Statue of Liberty) and a Toy museum.
If you are visiting southern France, then a visit to Monaco will most likely be on your list. Monaco is a great place and it is fun with children. For tips on places to visit, parking and how to see it in a day.