Is a private Normandy day trip from Paris worth it?
Be clear about the shape of the day first: of the nine hours, close to six are spent on the road. What you pay for is that the road is not yours to drive, and that the three hours on the coast belong to you.
It is worth it for families and couples who want real time at the cemetery rather than a slot in a schedule; for relatives of veterans, who often need longer at one grave or one stretch of beach than any group allows; for travellers with a single free day in Paris who want to see the American sector properly and be back for dinner; and for groups of four to seven, for whom the Van at €1,069, shared seven ways, competes directly with seven coach seats, with your own route and your own door.
It is probably not for you if you are travelling alone on a tight budget: a coach day tour costs far less, includes commentary and gets you to the same beaches, only on its own timetable. If what you want is Rouen or Giverny, the train is cheaper and fast, about 1h30 to Rouen direct from Saint-Lazare. With very young children, six hours in a car in one day is a lot to ask; two days with a night in Bayeux work better. And if you want the history explained as you go, add a licensed guide or choose a guided tour, because your chauffeur drives and waits but does not guide.