Renting a car in France
My sister and I are in our 70’s and have always rented a car in France without any issues. If you limit yourself to taking the train from destination to destination you will end up in the large cities ( which we avoid ) and will miss what France is most famous for: charming small villages.
As others have said, give yourselves an overnight at the airport on the night you arrive and start out fresh and rested the next day.
We have always rented a car at CDG using Sixt, Hertz, and AutoEurope. I am a Gold member with Hertz but cannot recommend them for CDG. Be rue to rent an automatic transmission. Plug your smart phone into the car and use your favorite navigation app. We used Waze this year and it worked very well even directing us flawlessly out of the airport.
Avoid the larger A roads, the France toll road freeways, unless you need to get from one area to the next in less than three or four hours. Using the A roads you will miss out on most of the scenery. Use the D roads. Pack Michelin maps for the departments you will be visiting and keep them in your car as back up.
Also buy a map of Les Plus Beaux Villages ( the most beautiful villages of France ). Do your online research and select which villages you want to visit. Look up the driving distance between each and then plan your day accordingly picking one with a nice selection of restaurants to stop for lunch.
Review the France driving/parking signs ahead of time and always watch for ‘Payant’ painted on the street and pay at the blue pay station putting your receipt on the car dash.
Jill