Add Normandy and Loire to Best of Paris in 7 Days Tour

Arrive one day earlier in Paris and head out to Normandy so you won’t be exhausted at the start of your RS tour. You will deal with jet lag on arrival day when you travel to Bayeux which is OK. It is your late night return to Paris on Saturday after what can be an exhausting tour that bothers me. Perhaps put Normandy at the end of your tour except then you will be tired from the tour. Definitely fly in a day earlier than you plan. There are many other historic and beautiful places to visit in Normandy..Monet’s Giverney, Etretat, Honfleur, Rouen, Mount St-Michel.
It is easy to rent a car in France. No different from the USA. Same for driving. We have driven all over France without problems. Just learn the European universal road signage.
What’s the must see in Normandy? Many! WWII history. D-Day landings, Utah and Omaha beaches, American Cemetery , St-Mere-Egliese and more! In Bayeux, visit the Bayeux Tapestry too, a must see!
When would you plan to visit the Loire? After your tour? That would be best. Separate from Normandy. You would need to more than double the amount of extra days. The tour is rather short so that would be a good idea.

Can you add days before the tour and after the tour? If so, take a train from CDG before the tour and go to the Loire Valley. You’ll then go to Paris from the Loire for the tour. After the tour go to Normandy.
Take a direct train from Paris to Caen and rent a car there then drive to Bayeux and sleep in Bayeux.
The must-sees in Normandy are the Port Winston Artificial Harbor, WWII Normandy American Cemetery and Memorial, Omaha and Utah Beaches. You need a full day, otherwise why go.

You could do the Normandy part as you outlined before the RS tour starts, but I'd suggest adding Saturday night in Bayeux instead of taking a late train back to Paris. The cathedral and tapestry at Bayeux are well worth adding some time there. You can ask Google whether the tapestry is open on Sunday morning. A midday train from Bayeux on Sunday should get you back to your tour hotel before 3:00.

You may already know this, but getting to Bayeux from CDG means going into Paris, the Gare St-Lazare, for a train to Bayeux. I'd suggest a taxi from CDG to GSL with four people and luggage. There's a way to do it by commuter train (RER) with a change, but a taxi will cost only a little more and be much easier.

After the trip, you could spend several days in the Loire. I'd suggest a train from Paris to Tours, or Blois or Amboise, then a rental car, which is the most convenient way to see the sights in that area. Focus on the area either east or west of Tours. You could drive the car back to CDG or perhaps pick up a fast train direct to the airport at St-Pierre-le-Corps, near Tours.

It's not hard to rent a car in France, though rental offices may have limited weekend hours in some towns. Auto Europe can help you find options. Driving is not difficult outside the big cities, though many local streets are narrower and curvier than Americans are used to (having been designed for horses and carts centuries ago). The "Explore Europe" and "Travel Tips" links in the upper left of this page can help you plan this trip.

Thank you Suki, MaryPat, and Dick for your helpful suggestions!

It is great to know France does not have the car rental shortage issues we have in the US. We were in Big Island few months back and waited for more than 2 hours for a rental car!

You may wish to check whether the Chateaux you want to see are closed Monday or more days, especially in April. Both additions you are considering involve outdoor time, including walking from on-the-grass parking possibly up the street from the Chateau. So you'll need foul weather gear for rain or shine sightseeing. We used books and a rental car (3 night stay), not Overlord, but they are so popular that they tend to book up in advance.

Gardens are of interest to us, which would still be bare in April. But you can expect smaller crowds, a plus.

It is a poor comparison, but like "Gettysburg" in the U.S., this is a very large area of history, that takes a lot of time to cover. You will have to see less than "everything", in a single day. That is fine for most visitors.

You are right to spend at least one night near the Normandy beaches, simply as a practical matter. It is not a suburb of Paris. I note that you did not mention the Bayeux Tapestry or Mont St. Michel.

https://community.ricksteves.com/travel-forum/france/normandy-brittany-thoughts

https://community.ricksteves.com/travel-forum/france/loire-base

https://community.ricksteves.com/travel-forum/france/day-trip-from-paris-to-d-day-beaches-acf8ace3-7773-4e57-b464-b178dcd45e1f

Have you looked into the Rick Steves Paris & Best of France tour? Clicks all your boxes but (either good or bad) adds a few more.

To build on ‘dovetraveler’s’ response, do consider signing up for the Paris and the Heart of France (HOF) tour which covers Normandy, several chateaux, MSM, and Giverny. It’s an excellent itinerary. You start with a few days in Paris and could add a few more at the beginning or end to do Versailles or whatever else you might want to see. It’s possible to do Normandy on your own (we’ve done it), but HOF is a very good alternative.