ok .. Got it.

In addition to the Michelin maps of the areas, get the Michelin Green Guides (Normanday), and do that NOW, before you leave. Look at the tours they recommend for the beaches for example, and maybe you will have a better idea of what is possible. I agree with St. Cirq about Pointe du Hoc (since you are tearing through). A sub might be Arromanches, and surely you will want to see Omaha at the least.
Even with a GPS I recommend a map where you can quickly see the whole surroundings--although maybe you can on your GPS. I can't, and I believe I would miss much just depending on "destinations" entered.
I really find this itinerary daunting, but as FMT said, it is your tour, not mine.

To get maps for your GPS, you buy them online from the GPS company's web site and download them to your GPS unit. Or, from the same web site, order the map(s) on a micro SIM or some such storage medium and have it mailed to you.