Loire Valley to Normandy Beaches

Renting a car in Tours and then using it for both the Loire valley and Normandy is a good idea, and in fact, I'd say first choice. I don't believe that Loire Valley tours include much education, they're mostly transportation for people without cars. Local guides in Normandy are very well versed in the WWII history there, but the informative museums at Caen and Bayeux would be good to include when traveling independently. You could drop the rental car at Bayeux or another stop outside Paris (Chartres, Versailles, Orly Airport, etc.), if Paris is your next destination.

We have a similar plan, but we want to go from Paris to Chartres, then Normandy, then Loire Valley. Apparently there is a car rental office in Chartres but (as far as I've been able to find out from an online search) they don't offer a car with automatic transmission on the morning we want to rent. Apparently instead of taking the train to Chartres, we'll have to get our rental car in Paris near our hotel and drive out to Chartres. This is not ideal because we're very nervous about driving in Paris.

Before actually booking, I'm going to call the car rental company (we've pretty well settled on Avis) and press them for an answer about car availability in Chartres. I suggest you do the same regarding Tours.

Also, here is Rick's page on renting a car in Europe:
https://www.ricksteves.com/travel-tips/transportation/booking-a-car

@epltd -- car rental at Orly should have a better chance of getting an automatic.

Just keep in mind, rental agencies don't promise a specific car, just a class of car. And it's quite possible that just before you get there, they will have rented the only automatic in their fleet.

I would suggest you be prepared to shift for yourself, and to try and at least learn the rudiments if you don't know how.

All of your advice is very helpful! Any suggestions for where to stay in the Normandy area? Is a trip to see Mont St Michel going to require an entire day?