We are interested in visiting Normandy for 5-7 days in early October. If we fly in/out of CDG, is renting a car better than train travel? We want to stay in Bayeux as a base to exploring the D-Day sights. We may want to add a side trip of 1-2 nights at Mont St. Michel also. In both cases, we would stay in the center of the city rather than the outskirts. It seems some hotels offer parking and we think we would like to visit D-Day at our own pace rather than sit on a bus. ( obviously it's a last minute trip ) We have been to France before but not to Normandy.
See this topic on this board, still an active one, re a concern like yours. There's no direct train service from CDG to Normandy. The drive takes several hours and might not be the safest way to go (for you or other motorists) after an overnight flight with little sleep. If you don't want to drive that first day, you could get into Paris (by RER, taxi, or Rossybus to the Opera Garnier) and make your way to Gare St-Lazare for a train to Caen, where car rental offices are close to the station. Then drive on to Bayeux. If your flight lands too late to make these connections the same day, or you're too tired, spend the first night in a hotel near St-Lazare and take the train in the morning.
Bayeux, just a short drive from Caen, is an excellent base for exploring lower Normandy, including the D-Day sites. Mont-St-Michel would be an easy overnight trip from there, or even a rushed day trip if you need to rush. But your overall time frame ought to be enough for all you want to do. Bayeux and Caen both have good WWII museums, Bayeux also has its fine cathedral and incomparable tapestry.
We stayed at the Novotel in Bayeux, about 15 minutes walk northwest of the city center, with zero charm but very convenient to the ring road and roads to the beaches. But Bayeux isn't that hard to drive in and out of, you could probably find something equally convenient closer in.
We took the train from Paris to Caen, rented a car there and stayed in Crepon for several days. Hired a private guide for one half day, and he gave us a terrific overview of the area, so that we could go back and do more exploring on our own. Drove to Mont St. Michel as a day trip, which we found do be very doable.
Earlier this summer, we arrived at CDG, took the Roissey Bus to the Opera House (I think), walked to our hotel near the train station, and took the train to Caen the next morning. We rented a car, visited the Caen Memorial (excellent) and then stayed in Bayeux to visit Normandy sites. It worked well, except the car rental agency was closed as it was a Sunday. Arrangements were made to get the keys from a near-by hotel, but locating the car became an adventure. In Normandy, we were really impressed by the German cemetery at La Cambe, and the World Peace Statue at Grandcamp Maisy. My husband, in particular, was fascinated by the Musee le Mur de l'Atlantique (a German observation bunker that was not destroyed and has original equipment), and Hillman Strong Point. They are somewhat out of the way, but offer a different perspective than the more visited sites.
Just keep in mind the plan to train to Caen and pick up your car there doesn't work if you arrive in Caen on a Sunday, as the car rental places are closed. Also check their lunch hour closing times which could give you a small delay if you're arriving in town then.
These are not big problems in the scheme of things, just items to be aware of to avoid being suprised and to maximize your planning.