Rent a car from Paris

Get it FROM the closest place to where you're staying (leaving the city is simple).

Finding a place to drop if off might be a bear if you've never driven in the city.

The obvious question then becomes: Where are you going after Normandy?

You can rent a car in one town on the way to Honfleur, then drop it off in another town. As long as the 2nd town is in France, you will not pay extra to drop it off in a different location from where you picked it up.

Edit: Rouen is one of many options for pick-up

We always take the train to Caen, about 2 hours, and then have a car booked and waiting at one of the four rental agencies right across the street from the Caen railroad station. All are open on Saturdays until noon, maybe later, unlike rental agencies in smaller towns. You will miss any hassle of returning to Paris in clogged motorways which can occur as locals return from a weekend or holiday away. There are some delightful B&B's in Normandy, not far from Bayeux that are easy to find and much more fun than a hotel.

Ann, my son and I did this trip last summer. Picked the car up at Les Invalides and, since we were returning only to Paris to fly out, dropped off at the airport. The prices are much cheaper if you pick up in the city, rather than at the airport, but no extra charge to return to the airport. If you do that, however, it is really difficult to find the rental car return at CDG so allow extra time.

I can't help you with where to rent the car from in Paris (we are renting near the Arc D' Triomphe, because it was available the hours we needed it, not too far from where we are staying, and looks easy to get out of town), but I do want to suggest that you price it carefully if you pick it up out of town. I found it a lot more expensive picking it up even someplace like Rouen (and then add the train to get there) over picking it up in Paris, the city (not the airport.)