Need help in mapping our trip from Soutwest France to Nice

You're asking for a lot of help; and it appears that you haven't done much spade work. First recommendation, therefore, is go out and buy a good guidebook. Your choice of destinations looks good; but with no clues about your interests, it's hard to make recommendations about what to see. Also, you need to define what a moderate price is to you. I suggest you go to booking.com to get your lodgings. You're going soon, and you're a little tardy for reserving. When you put in your dates at booking.com, you'll see only the places with availability, as well as prices and reviews. Then, you won't be dependent on one person's evaluation; and you can choose a price that suits you You'll also get instant confirmation. An added advantage is that you'll then have your reservations all in one place. I'd pick up the car at the train station of the first southern destination and keep it until Nice. Generally speaking, there are no drop fees, if the return is in the same country; and the per day charge is less, the longer you keep the car. Getting around in Provence is easier with a car than trying to do it by train. We usually use AutoEurope for cars, and have been very satisfied with our experience. (If you're unfamiliar with them, come back for an explanantion.)

Driving is more flexible for the majority of the trip. I'd start with booking your hotels at both ends, and booking those two train rides at http://ricksteves.raileurope.com/us/rail/point_to_point/triprequest.htm. On the SNCF site, the cheaper rates are sold out from Nice to Paris on June 9, and it's hard to book other rates there with US credit cards, unless you have Verified by Visa or MasterCard SecurCode.

Can you stay in Paris at the start? DB schedules only suggest one connection plan from CDG to Sarlat in the afternoon, assuming you can leave the airport by 13:00 (by RER & metro connection or by Air France Bus #4 to Paris Montparnasse station), and stay on schedule to catch the 14:46 at Montparnasse. I think that's cutting it too close for comfort.

If things really are "subject to change," then you should look at flying into Toulouse. it will save you a ton of time and let you visit someplace else great on your way to Provence. Or, get your Paris time in first and fly home from Nice.

It also looks as though you are planning exactly one full day in the Dordogne. This is not worth the difficulty of getting there and on to your next destination. I'd say 4 nights minimum, or bag it and spend the day someplace else. Honestly, do not kid yourself about the amount of time involved getting to and fro.

I would say that you do not really have enough time to cover all this ground. Personally I would trade Nice for the Dordogne in a heartbeat, but chacon a son gout.

To expand on what Adam said . . . you can get a sense of how long the drives are between your destinations by going to www.viamichelin.com. Their times are minimum estimates. People suggest adding as much as 25%. You will be surprised at how time-consuming short drives in Europe can be, if you're navigating on hilly, twisting country roads.

Thank y'all for your advice. Thus far:
- I've bought a 5-day RailEurope pass, starting on May 27
- Upon arrival in Paris (May 26), to stay overnight in Novotel Gare de Lyon so we could catch an early train ride to Nice
- Booked 3 nights in Novotel Montparnasse (6/9-6/12)
- Booked 1 night in Novotel CDG prior to US return on 6/13
Now, I'm trying to figure out (with 5/27 to 6/1 nights)
- where to stay in Nice (Central or close to the TGV train station. (any hotel suggestion?)
- how long do I need to stay in the city before I go off driving to the small villages
- Can you map for me which villages are interesting (NOT wineries), with historical sights/markets; where to start and end?
Plan on taking the train to Avignon on 6/2, and need recommendations on:
- accommodations, where & how long to stay before driving out to small villages
- mapping out interesting villages (first and last) before we head back to Paris on 6/9 via TGV
Thanks so much again!

By the way do we need an International Driver's License to drive in France. We had in the past obtained one, but I found that the rental cars never asked for it when I picked up the car. The last I drove was in UK in 2010, so I don't know if there are new driving requirements. Thanks.

I am not certain that you need one, but it is surely not a bad idea. You can read here, and get from "Triple A".
http://www.aaa.com/vacation/idpf.html