Hi from Wisconsin,
Full day, no doubt.
I know this sounds extravagant but an overnight in Bayeux the night before the tour might allow you to see the Bayeux Tapestry and walk the old town. If you are unfamiliar with the tapestry, it is a very long (70 meters) embroidered cloth. It tells the story of the Normand invasion of England. They believe it was completed 16 years after the invasion, perhaps as propaganda justifying Normand inheritance of the English crown. What it does do for historians is show how horses were transported across the channel, armor worn by worth sides, and head hair styles along with oh so many other things.
See what time the tapestry opens or closes and when your D-Day tour begins or ends.
One of the few cities in Normandy that was not heavily damaged during WWII. It had very little damage. it was captured so quickly no battles took place inside the city.
wayne iNWI