Tough Itinerary

I would favor staying in Paris at the start. You will not have to do any driving right off the plane, can recover from jet lag, and get a relaxing start. I'd probably combine Mont St Michel and Amboise with a single car rental, perhaps taking the train to Rennes, then renting a car for a few days to go north to Mont St Michel, then south to Amboise to cover that region.
Now you have a choice of driving to Provence or taking a train. Train would be quicker, and remember that fuel and tolls are a lot higher in France tan in North America. You could drop the rental car at St Pierre-des-Corps and get a train to Avignon TGV and rent another car there. That could be done in 5 hours. You would have to make a station change in Paris from Gare Montparnasse to Gare de Lyon. That can be with a bus or Metro, but maybe a taxi would be smoother.
You could also hang on to the car and drive there. There is so much to see, it might take a couple of days. Don't worry about finding places to stay. There will be lots of options.

Change the order:

Paris
Provence
Amboise (You can avoid Paris by going Amboise to Le Mans then Le Mans to Rennes)
Mont St Michel
Return to Paris

Versailles & Chartres can be day trip from Paris

There is a direct TGV train from St-Pierre-des-Corps at about 14:30 daily that runs to Avignon TGV station and to Marseille. You can pick up a car at either place, or continue to Arles by train if you don't yet need the car.

However, if you want to drive in both regions, it can be cheaper to keep the same car at a weekly rate (5, 6, or 7 days usually all the same price). The major agencies rarely have any significant fee to drop at a different location within France. www.autoeurope.com is a US consolidator that reps several agents.

Our tours have sometimes used Le-Puy-en-Velay as a nice town for an overnight; it's about 2/3 of the way along your route, certainly not the only option in the region.

I would fly on to Provence the afternoon you arrive or perhaps take a train. End in Paris. do Mont St. Michele as a side overnight trip from Paris. You could also do the chateaux of the Loire as a day trip from Paris -- Go to Tours and join a mini van tour. Otherwise you will need a car and you don't have time to drive the length of the country.

Would this work?
June 21. Arrive Paris. Train to Chartres (1N)
June 22. Pick up car. Drive to Loire Valley (2N)
June 24. Drive to Mont St Michel (1N)
June 25. Drop off car in Rennes. Train via Paris to Arles (5N)
June 30. Train to Paris (6N)
July 06. Depart Paris

There is a direct TGV from Rennes to Nimes that you may also like to take advantage of.
TGV 5348
Dep 09:10 RENNES (France)
Arr 15:01 NIMES (France)

Two years ago we rented a car in Paris and drove to MSM (2 nights) via the Normandy beaches. We took an afternoon while in MSM and visited Cancale (well worth it) and then went on the Amboise for 2 nights before heading back to Paris (via Chartres). It was more time consuming to drive than I anticipated. In hindsight we spent too much time driving. Also, after seeing numerous major sites in Paris, Versailles, the Abbey at MSM, and Chenonceau near Amboise, by the time we arrived in Chartres it didn't seem overly special.

Hi, this is the original poster. Thanks for all of your helpful suggestions. We determined that once we were driving, it didn't make sense to mix trains and car because of the way the trains operate. I have some new questions. Based on your advice, this is what I have decided to do:

Wednesday, June 20th: Arrive in Paris. Stay 5 nights in Paris.
Monday, June 26th: Stay overnight in MSM
Tuesday, June 27th: Drive from MSM to Loire. 2 nights at Saint-Georges-sur-Cher.
Thursday, June 29th: Drive towards Provence. Stay overnight in Chaspinhac.
Friday, June 30th: Arrive in Provence. There are 3 possible places we have booked: Maison d'Hotes Douce (Comps), Le Mas Ferrand (Graveson), or L'Oustau de Mistral (Eyragues).
Tuesday, July 4th: Drop off car at Avignon & take TGV to Paris. 2 nights in Paris.
Thursday, July 6th: Fly back to NY.

Questions:

Should we rent a car in Rennes & drive it to Mont Saint Michel, or take the shuttle to and from MSM & Rennes, & rent a car at Rennes after returning there from MSM? Is it good to have a car at MSM?

Is it incovenient if the hotel in Chapinhac is outside of the town? It is a 10 minute drive to Le Puy-en-Velay and the Routes of Santiago de Compostela.

Of the 3 places in Provence I listed, which are the best locations? Would you recommend any of the particular hotels I booked?

Does it make sense to stay at one of the Provencal places I booked a few nights, then drive to Roussillon & spend a night there before returning to Paris?

Again, thanks for all of your previous help. We would appreciate your advice.

Mixing train and car can make a lot of sense if it
- reduces the time taken to travel a long distance.
- saves money on fuel and tolls.
- saves headaches with traffic, navigating, parking.
- means not paying for a car to sit idle at a destination where public transport is preferable to use.

And:

• Reduces the risk of speeding tickets and ZTL or bus-lane fines.

Just know, when renting a car, you need to know how to use toll lanes and booths where USA cards with chips may or may not be accepted.

See

http://www.francetravelplanner.com/trans/car/tolls.html

And, also know to always top up the tank, and not leave it for Sundays, etc., anytime (pumps don't accept cash) inside is not open with a clerk.

Thanks for all of your responses. These are helpful in balancing car & train & knowing about renting a car. So much to think about, but so interesting!

I will try to answer your question on where to stay and what to see while in Provence. As I understand your itinerary you will be staying four nights in Provence and will have three days for sightseeing. That seems a very reasonable plan - of course more time would be even more reasonable.

You mention that you would like to see "Arles, Roman stuff, Les Baux, hilltop town like Roussillon". All of these places are easy drives from any of the places that you have reserved so I would just choose the one that seems most appealing to you. Les Baux would satisfy my need to visit a hilltop town so I would cross Roussillon off my list.

But I would add a few places for your consideration:

Pont du Gard: an outstanding Roman aqueduct.

Orange: Roman theater still in use today.

Glanum: Roman ruins and an area that Van Gogh painted olive trees.

Thanks, your reply is really helpful. I was planning to go to Pont du Gard and now I am considering Orange & Planum as well thanks to you. I'm not going to stay in Roussillon, we'll spend all 4 nights in 1 place. Thanks again!