I'm back, with a bit more detail and still seeking advice...
We (me. wife and two boys age 10 and 12) will be in France from 8/18-9/2. We have never been to France. Paris is already booked for 4 nights from 8/18-8/22 and Chamonix is booked from 8/28-9/2. We fly into Paris and out of Geneva. This part of itinerary cannot be changed.
So how best to develop an itinerary for the middle six nights, 8/22-8/27? I think we've narrowed down our options to either train to Avignon and tour some of Provence (perhaps split bases in Arles and Luberon areas?) OR train to Stasbourg (or another hub in that region?) and see the sights in Alsace/Bugundy regions while making our way south to Chamonix. In both cases, i think the plan would be to rent a car in either Avignon or Strasbourg and then drive on to Chamonix.
I think our goal for these 6-7 days would be to experience quaint/walkable towns, see some good historical sites (castles, ruins, etc.). and enjoy pretty countryside. We don't need/want more big cities as Paris will cover that...
So thanks in advance for all your great tips and insight!