Realistic itinerary for Normandy?

We have been to the Normandy area several times, and IMO one day to explore the D-Day sites is not nearly enough. At the bare minimum, I would add a full day to that portion of your itinerary.

emilyjoylee,
My only comments here:
Giverny is small, and car rental options would be sparse.
Driving to Rouen after morning at Giverny...you would hopefully arrive mid or late afternoon, giving you time to walk around the centre-ville and see the Cathedral there. Parking in Rouen is a real problem, so perhaps instead, take a train to Giverny, then next day a train to Rouen after a morning at Moinet's gardens, and renting a van in Rouen the next morning to get to Bayeux. (Don't know about van availability.)
Leaving Rouen in the a.m. should get you to Bayeux in time to visit the tapestry and maybe the cathedral there that day, then all the next day to visit some D Day sights. Don't be discouraged by comments that you need to spend multiple days there and visit every sight. Not everyone wants an immersion experience. We have always driven ourselves and felt we saw what was important to us in a day. (WWII museum, Omaha Beach, Amnerican cemetery for flag lowering, plus stopping here and there to wander around). It is up to you.
Another thought...if it works for you, you could return your van in the MSM area and take a train to Paris. That seems to me to save you time, unless you want to meander your way back to Paris (not an unpleasant plan!) and drop the car at, say Chartres or Orly and take the train or metro into the city....???

All of these are all some of my favorite places (I go to Normandy at least every other year). However, it seems slightly rushed. If I were advising a first time visitor, I would add another night to Bayeux and the Normandy Battle areas, and sadly forego Mont-Saint-Michel. You can easily fill two full days (i.e., three nights) in Bayeux—particularly if you have an interest in both WWII and the tapestry Your arrival drive to Giverny and then going to Rouen sound like a good plan. Don't get me wrong, I love MSM and have stayed there twice (plus one drive-by last June en route from Saint-Malo to Sainte-Mère-Église). But with so much to see in the Normandy Beaches area, and the complications of moving around anywhere with eight people, I would just save MSM for another trip. Alternatively, you could skip Rouen and rush to Bayeux. My too sense...

In my opinion, Mont Saint-Michel is the most important place on your list. It's one of France's iconic sights and there's nothing like it anywhere else. Not to be missed.