Help with Normandy planning

Rather than drive around and just look at the D-Day sites, I'd suggest taking one of the excellent local tours, many of which depart from Bayeux. You'll learn far more with a knowledgeable guide, so it will be a much more interesting and rewarding experience. If you decide to take a tour, pre-booking well in advance would be a good idea.

As you may be aware, for driving in France you'll need either an International Driver's Permit (which is used in conjunction with your home D.L.) or a certified translation of the terms of your D.L. in French.

I agree that a tour would add so much more to your visit to the D-Day sites.
I did an all day tour booked through viator.com, but they are consolidator and they actually booked us with overlord tours.
Stayed in Bayeux and enjoyed the town and sites there too.

If you plan to spend the night in the MSM/Dinan area I recommend La Jacotiere. Absolutely delightful with views of the Mont. If interested PM me and I can send you our blog of 3 days in the area.

Have to say that Rouen is not an easy place to drive through, so prepair well how driving to your hotel and the options where parking the car. Between Giverny it is worth having a stop in Andelys for the stunning view over the Seine Valley from Château Gaillard (skip the payed part, it adds nothing) and lovely Lyons-la-Forêt. Getting to the two places is quite time consuming but worth to consider to my opinion. Instead you can also make a little detour from Giverny to nearby La Roche-Guyon.

On the way back to Paris you can visit Fougères, Vitré, the much overlooked but stunning historic centre of Le Mans and ofcourse Chartres.

You can drive the WWII sites on your own but even though we had a car, we took an all day tour to make it easier on ourselves. The Overlord tour group was small and while we generally shun tours, this one worked well for us. Some other places we visited in our 5 night trip:
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We really loved Etretat and are sorry we didn't get to St. Malo. We intended to spend another 5 days in Normandy/Brittany this fall and spend some time in the St. Malo area, but I ended up getting surgery in Menton and so we had to cut that 5 days out of the trip.

I think you would be better off taking the train from Gare Saint Lazare to Vernon, visiting Giverny at your own pace, then taking another train from Giverny on to Rouen. I like Rouen, I think you can spend a full day there (so stay the night after you leave Paris and one more night to give you a full day). Rouen is the biggest city in Normandie but what you want to focus on is in the old center, so a car is more of a pain than an asset. The next morning, you can rent a car and start driving.

I think you are missing some sights, Etretat/Fecamp - up the coast - are the sight of some great cliffs (many German defenses were left abandoned/unattacked at the top of the cliffs. Etretat has a little more of a tourist industry, beach community. Fecamp is more of a regular working town/port.

Honfleur is a great old port town that is really popular. It's where the Seine meets the sea. I think you would want to visit, a nice stroll and lunch at an outdoor cafe would be ideal, but expect it to be crowded in the summer months.

If you are interested in D-day, Caen has the best museum and a few other sights. Bayeux is a great place to get a D-day tour and it's a nice town. My favorite sight in Bayeux, however, is the tapestry that documents William the Conqueror's conquest of England in the 11th century - figure maybe two hours to visit.

Mont-Saint-Michel is the last sight in Normandie. I think you may really enjoy a guided walk in the mudflats during low tide as well as climbing the ramparts up to the Abbey. I love the island but the middle of the day in the middle of the summer may be too crowded with tourists - try to get there early or late but give yourself time to see the Abbey and, if possible, low tide (and watch some of the tide coming in).

After that you will be in Brittany. If you are going to Dinan, you may want to stop in St. Malo, which has a nice rampart and beach. At low tide, you can walk out to some small fortified islands. The small beach is sandy, rather than pebbles, and is really popular in summer.

When you're done. You will save time and hassle by dropping your car outside Paris and taking the train back in. I think Rennes might be a good choice. A little bigger town will make it more likely the rental car drop off will have longer hours. In smaller towns, and even big ones, it's not unusual for the agency to close for a long lunch, maybe 11:30 to 2:00. If you're having trouble making a pick up or drop off reservation, try after 10 am and before 5pm - excluding the long lunch hour. Places are open longer than that but those are hours you can pretty much count on. Search engines will show pick-up/drop-off unavailable if the agencies aren't open at the time you put in.

If you're going to have a car for Normandy, I enthusiastically recommend a private tour with Chris of Visit D-Day. He gets in your car and navigates and narrates, while you drive, offering a less expensive option and the opportunity to personalize your tour. He occasionally had us pull over along the side of the road as he pointed out things we'd never have noticed otherwise, and covered way more ground than a group tour could have.
He's a retired Royal Marine, wife is Royal Navy and he has two adorable little girls. We spent a day last June with Chris and it was money well spent. He and his wife run a B&B, as well, but it's a bit off the beaten path. We chose to stay in a VRBO in the center, pedestrian section of Bayeux and it could not have been more perfectly located. Walking distance to everything.

Thank you all for your helpful responses! I am open to a guided tour, and would have to balance that with exploring on our own to avoid overlap and make the best use of our time. I will re-look at options to take in some of the other suggestions. So much to see and so little time!

We will have an international drivers' license (good thought to remind me!). As far as the rental car (and to give us more time in Rouen as recommended), I've thought of going to Versailles via train the day before our 5 Normandy days, then renting the car from there and driving to Vernon (Monet's garden) then on to Rouen. Then we'd explore Rouen and stay another night there before heading to Bayeux. (this does not allow time to explore sights enroute between Paris and Rouen - sigh. Too little time!) Exploring around the area (including some of your suggestions) would have to occur during the 2 days at Bayeux. Have any of you done this (rented car at Versailles)? Your recommendations?