I would honestly take a car. I live abroad and my parents live in Normandy. Until they create direct trains from CDG to Rouen/Le Havre/Caen (in 2009 at the earliest, in 2020 at the latest), taking a car is the fastest and most convenient way.
If price is the #1 factor then I would go for the train, as TGV advised.
Hope that mappy link will work
http://www19.mappy.com/sidyyU/SSFPQ8...pcv3=&ccv3=250