Normandy on May 8?

You can check the website, en.normandie-tourism.fr

There is normally special events in the area with notable people attending on V-E day. Especially at the American Cemetary. Maybe Google that topic to see what’s on the calendar.
As long as you arrive early enough to the cemetary, you’ll be okay entering.

Being a national holiday most of the museums there will be closed. Check their websites.

The beaches themselves are never closed unless there is a very high-level dignitary visiting (i.e., a head of state). And even if so, the area of the D-day beaches is a huge area—45 miles as the crow flies from Utah Beach to Sword Beach. And there are many, many more sights to see inland that relate to the battle of Normandy. I also doubt there will be something like a high-level visit that date in Normandy itself. But you can count on it one month later on June 6th (with ceremonies continuing through June 9) when it will be the 75th anniversary of D-day.