We are looking for a private driver for 6 to Paris or a tour company that you have had experience with.
In addition to any replies you get here, be sure to look at Cruise Critic. Here's their France Ports Forum: http://tinyurl.com/cdbsfhn
There are frequent trains between le Havre and Paris. It may be easier to book a guide in Paris than one from the port to Paris. Have you thought of that?