I plan to visit Paris in June with son and grandson (12). Best cost effective trip to Normandy. Go to Caen and select a tour or go to Bayeaux and select tour???
You'll need to book a tour in advance. Most of the tours depart from Bayeux. For the best experience you should spend at least one night up in Normandy. If you absolutely cannot do that, the best suggestion I have is to check with Overlord Tours to see whether it is offering its special full-day tour for folks staying in Paris during your time frame. I do not know how frequently that tour runs. I believe it departs right from the Bayeux train station, and it leaves just a bit later than the tours departing from central Bayeux, so it works for people taking the early train from Paris.
Bayeux has a picturesque historic center, a nice cathedral, a relatively new Invasion Museum and of course the Bayeux tapestry, so it is very much a worthwhile destination even aside from the D-Day tours available there.
I looked at your other posts about your trip and didn't see how long you'll have in Paris?
I'd also agree not to try and do this as a day trip. Spend one night in Bayeux, 2 if your trip allows that.
I've toured with Dale Booth who is very good and apparently good with kids but he gets booked fast. Many on this forum have done trips with Overlord and have excellent reviews.
TBH, I was a little disappointed with the museum in Caen which is a Peace Museum and not a WWII/DDay museum. I'd spend time doing outside sites over spending time in this museum. I have not been to the museum in Bayeux.
Last time I looked, no train from Paris arrived in Bayeux early enough to catch a full-day tour (which is very much the way to see this history.) Of course there may have been changes or exceptions to either train or tour schedules. Caen offers more choice of hotels and restos for an overnight stay and is a quick commute to Bayeux. The Caen peace museum gets good reviews and runs tours.
I believe that Overlord has a tour that meets the Paris morning train in Bayeux and returns people to the last train back to Paris. If you have time, it would be well worth it to spend two nights in Bayeux -- do a full day tour on the full day -- see the Bayeux Tapestry and Cathedral. But if time is very short look into their shorter tour. I have only done the full day tour, but read on line about someone doing the tour formed to accommodate day trips by train from Paris -- check with them to see if it available when you want to go. And you do need to arrange these things in advance. We did it in late October and there were already sold out tour slots.
If you haven't already, find out how interested your son and grandson are. Dale Booth does a marvelous two-day tour of the American sites but he may already be booked for June (Overlord probably has something similar). We took Dale's tour plus a day seeing the Bayeux Cathedral/Tapestry. When I plan a trip I consider the cost in money and the cost in time and the depth of my interest. Note that nights spent in Bayeux will cost less than those in Paris.
When i went to Normandy I went to Mont Saint Michel and slept in Dol de Bretagne (bus to MSM). From there you can easily visit Saint Malo and Dinan. Nice state!