My DS and I will be going to Europe next year and we are looking into tours of Normandy. I found these, which seem to be pretty good.
https://www.normandy-sightseeing-tours.com/d-day-tours/full-day.html
We are planning the half day Juno Beach tour (my DS will be 12 and even though he's very interested in WWII history, I think a half day is enough for him). We are doing the Juno one because we are Canadian. If you are planning a full day, or would like to do 2 days of tours, I imagine staying in Caen would be better, but we will be doing it as a day trip from Paris.