Mezt Flea market is a fabulous market that could rival that of Tongeren in Belgium. You can get everything you would want here from china/pottery to antique furniture to fabrics to collectables.
It's an indoor market that's in a collection of buildings called the Technopole on the southeast side of town. This is a great option as it's easy to reach by car and, as it's cash and carry only, you'd need one.
Visiting the Verdun battlefields while you are on a driving holiday is a good option as it will allow you to be flexible and go to places where larger tour operators either don't have time to visit, or cannot get to due to the size of their vehicles.