car rental outside of Paris convenient to rail line to CDG and Paris and Normandy

I would rent from an agency near les Sablons or Pont de Neuilly métro stations. They are easy to reach and driving is extremely simple, just proceed due west to A14/A13. Rent from an agency which does not charge for a drop-off different from pickup. I like Sixt for Europcar for this.

I don't really know the details but CDG has limited rental car pickup to newly arriving passengers, not to mention CDG is on the wrong side of Paris to reach A13 to Normandy.

Thanks. We'll check into it. I only mentioned the airport because we have to get back to it (we have a hotel there that night before we fly out ). Is the traffic bad getting from the metro car rental out of the city?

In 2017 we picked up our rental car at CDG after arrival from the states and drove to a relatives home outside of Paris. We returned it 3 weeks later at CDG the day before our flight home without a problem. (We stayed at an airport hotel that night.) Our traveling companions (family members) picked up their car at Orly after being in France (Paris area) for a week, and returned it to CDG 2 weeks later without any problem. Following the signage at CDG to return the car was not easy, but we made it. You can do this.

It depends on where in Normandy you want to visit. You can get trains from Paris to Rouen, Caen, Cherbourg (all from Gare Saint-Lazare) and Rennes (from Gare Montparnasse), and all have rental car options. You could then return to CDG, but check if the rental company you use has a drop-off fee.

Might as well just drive the car to CDG, which has no direct train connection with Normandy. We drove from Bayeux to CDG, it wasn't pleasant through the Paris suburbs but it was no worse than comparable driving around US cities.