I highly second the recommendations for AutoEurope -- we rented from Hertz and were not pleased. Previous times we've used AutoEurope and had pleasant experiences. We picked up our car in Avignon (a different travel plan than yours) and had it for 10 days, returning it to Paris at Gare de Lyon. That was "an adventure" but we survived it. You can drive in Paris if one person in the car is an expert at reading maps, signs, and has a good sense of direction. Make sure the AutoEurope people give you good directions to where you are returning your car and there will be no problem. We were not so lucky with Hertz, but we survived.

LVSue: To clarify, I don't know of any Air France shuttle that goes to Austerlitz - far as I know, the only stations they service are the gares de Lyon and Montparnasse. A private shuttle service would take them anywhere.

elizabet: Navigating to the Invalides drop-off spot shouldn't be too terrible with detailed directions and a good navigator.

St. Cirq, elisabet was talking about a private shuttle, which will, of course, take you anywhere you like.

Elizabet, you may be right. Even if it takes you 2-3 hours to get through customs and to Austerlitz, that's a bit of waiting. However, I did a double check on SNCF and there are trains at 9:09 and 10:11 also. I had used another source before because SNCF gives me fits too. It looks like there's a "Prem" rate of 30 euros second class, though traveling with children under 12, four of you can get a 25% discount anyway on either 1st or second class.

Anyway, it seems as if you have decided on Paris for two days, and that's OK too! I just didn't want you to make your decision based on my erroneous first post.

At this point, I am working on a variation of the TGV plan. TGV from CDG to Tours. Then a rental car, already reserved with Auto Europe. They said the pick up/drop off plans could be changed. Sure hope this is true!
But I am a bit confused about whether there is a train change at St Pierre de Corps. Or is that just a stop?
I would like to pick up the rental car in Tours, drive to Chenonceaux for one night and then drive to the Dordogne the following day.
On the return, we would drop the car in Tours or Chartres and take a TGV to Paris.
Is this doable?