Lots of things to see there and the structure is amazing - was intended as a V1 and V2 rocket launch site across to England.
Some of the displays and videos shown have some very graphic images of the holocaust though so you have to be careful if you have sensitive children, but the staff warn you of that in advance anyway. Our 9 year old was doing WW2 at school so this was very interesting for her, and our 4 year old son loved the rockets on display.
We went LD lines to Le Havre and stayed in Homfleur at the end of November 2 years ago. We visited Pont du Hoc, Long sur Mer and several others. Pont du Hoc in particular out of season as many fewer people and much clearer skies in November. Homfleur in late November was truly magical plenty to do in a long weekend we got the Thursday night 11pm boat out and Sunday lunchtime boat back.
We had 1 day this year, had booked into a B&B for 2 nights on the way back from the Vendee - wished we had longer really. First we went to the Omaha beach museum, which also had a good film that we watched. Then we spent some time at the American Military cemetery - very moving, again the visitor centre there showed a film. We then spent a good number of hours on the beach letting the boys play, it was a lovely sunny hot day. Did a few more sightseeing things like a quick stop in Arromanches and also somewhere that I cant remember that had these bunker things still standing.
We've taken our sons to a few WW2 sites around the Calais area and Germany already. One of them is interested in seeing Omaha beach, it's a topic at school this term.
Is there enough in the local area to make it worth a trip? Museums etc or would you just end up parking at the beach, getting out look at the beach, then get back in the car again?
We could do an out of season weekend Brittany Ferries break and take the car. Or make it part of our summer holiday, we're heading down to the SW anyway. The weekend break would work if there were enough similar things to do near by. They would love the submarine and sea life centre in Cherbourg.