Help with my itinerary / Normandy

Well that is a very short, focused trip. The one glaring omission is the D-day areas. You say you will "visit Omaha Beach." But the beach itself is only half the story and you won't even devote a half a day to this area if you want to go to MSM the same day. Smart of you to stay overnight near MSM, but consider allocating another day to the sites associated with the Battle of Normandy. Maybe go to MSM Sunday evening and spend all of Friday and Saturday in the D-day areas? I promise you it won't be too short a visit. I can't comment on Versailles as I have never been there and the reported crowds and lines really don't appeal to me. BTW, the drive from the Normandy Beaches to MS is fine, but not overly scenic. A stop in Avranches for a bite might be a nice diversion. Enjoy!

Many thanks for your comments. My teenagers not so interested in WWII history but I want them to visit the American Cemetery and Omaha Beach at least. I´ve been there a long time ago and thought it was very interesting.

There is a very good museum at Utah Beach, if that fits within the parameters of your itinerary.

You've noted your teenagers aren't particularly interested in WWII. In addition to mentioning what they're not interested in, could you share their interests? What would they find interesting? Is that the "small villages and nice views" part or is that you?

A few things off the top of my head:

• Either on the way to or back from Mont-Saint-Michel, consider a brief
  detour to Fougères to see the château there. It's one of the largest
  medieval defensive fortresses in Europe.

• Consider passing through the medieval town of Villedieu-les-Poêles
  and stop at the bell foundry Cornille Havard. They present tours in
  English and it's a fascinating look at how bells -- some probably as
  tall as you -- are made. The techniques, beyond a few electric tools
  and modern safety gear, seem to not be that different from those used
  in the past. Bells from Notre Dame de Paris were refurbished there
  after the fire.

• If you visit Villedieu, a short drive north is the scenic valley near
  Hambye containing a ruined abbey. It's a peaceful, green place to
  visit and the ruins might remind your teenagers of some of the sets
  from the Lord of the Rings films. There's a terrific auberge right
  next to abbey for lunch or dinner.

• East of Hambye is a former viaduct (viaduc en Français) in the steep
  valley of the Soulevure River: Le Viaduc de la Souleuvre. Depending on
  their risk taking tendencies, your teens could take a fast luge down
  the slopes or bungee jump from one of high piers remaining from the
  viaduct.

• One of the castles of William the Conqueror (Guillaume le Conquérant)
  is located in his hometown of Falaise. It boasts a self-guided tour
  and is located next to a museum highlighting the lives of the people
  of Normandy during WWII. The short film displayed in the ruins of a
  former residence is well done.

And since you'll be driving, a quick note on speed limits. In general, roads in France are pretty poorly signed for speed limits, as the French driving regulations stipulate maximum speeds depending on location, weather, and road characteristics. The assumption is that drivers know those rules, and speed limit signs accordingly are less common than in many other countries.

On roads outside of cities that are not divided highways the default speed limit is 90 km/h in the département where Caen and Bayeux are located (Calvados). However, it's 80 km/h in the département where Mont-Saint-Michel is located (Manche).

On the drive back to Paris from Mont St Michel you have a couple good options. Le Mans, which you should visit if there's any interest in racing cars, or Chartres, for the cathedral and history. Both are easily worth a day or more.

Be aware that the Normandy American Cemetery closes the gates at 4:30PM.