I would devote some time to seeing D-day sights you saw on the tour which you wish you had more time. Plus there are several good museums. IDK how much time or how many museums the tour will include, but I can't imagine they spend many hours at any one museum. If you are interested in American sites, some of my favorites are The Utah Beach Museum, The Airborne Museum in Sainte-Mère-Église, The Overlord Museum outside of the American Cemetery entrance, The Bayeux Museum and the Azeville Battery. You will likely stop at two cemeteries briefly on your tour. I recommend seeking out others. Two that I find contemplative but aren't on everyone's trip are the Bény-sur-Mer Canadian War Cemetery in Reviers, and the German Cemetery in Orglandes (not the one right next to the highway that everyone goes to).
Non-WWII sites I recommend that are within reach of Bayeux are the Bayeux Tapestry, Mont-Saint-Michel (spend the night on the island), and the town of Avranches. Further East and heading towards Paris, are Rouen and its medieval center, the ruins of Abbaye de Jumièges, and the Castle of La Roche-Guyon.