Just for the record, the coach bus tours are more than just driving by and looking out the window. All of them, even the 1 day quick ones like I did, give you a fair amount of time to wander the beaches, the cemetery, and museums. Obviously you can’t spend hours in one place but you are seeing these historic places mostly on your feet, with the bus being the means of transport between them.
Smaller tours like Battlebus use small vans with about 8 people and give you more time and more stops. I think you can find a tour to suit your needs no matter who you are. If you do it on your own you must have done your research. That is great. I would just not want to miss something I could have seen and not realize it until back in the States.
Keep in mind that driving in France also can be an adventure. I lived in France for 2 years and had my own car so I know how the frogs drive. It takes a while to get used to the flow and chaos, at least in the larger towns.
My car rental company specifically instructed me to NOT to drive l’Etoile, around the Arc de Triomphe, but otherwise, I didn’t find Parisien drivers any worse than New Yorkers.
In fact, Parisien freeways are safer than Cleveland’s.
As far as Normandy is concerned, driving about is easy as pie. No different than any other rural area.