Normandy

Haven't been to Barfleur, but was just in Honfleur for 3 nights last month. Absolutely loved it. The Basin and the town itself are a lot of fun. You could then go to Bayeux and stage your D-Day tour from there, where many of the tours leave from anyway.

Assuming you have a car and aren't trying to have a "slow-trav" experience, you could do something like this: Day 1, leave Paris early, be at Giverny when it opens-a visit needs about 2 hours, drive to Rouen for a late lunch next to the cathedral (enjoying Monet's views of the place) and a walk along the main drag from the plague place (don't remember the name but it's a few blocks east from the cathedral) to the Jeanne d'Arc site, late afternoon to Honfleur...........Day 2, drive to Bayeux and see the tapestry, picnic and contemplate on Omaha Beach, visit the American Cemetery, on to MSM for the evening, staying there or nearby. We didn't make it to Barfleur (I wanted to visit it because of the White Ship connection)..........Day 3, drive a bit farther to St. Malo (you could do Dinan instead but St. Malo is a lot livlier), then head back to Paris.........this may be too fast paced for some, but we enjoyed doing this a couple of years ago. You could, of course, skip the additional sites if you prefer to linger.......A few other comments: Dinan fits your description of quaint with a bit of nightlife but it is more of a small town. If you had another day, you could visit Fougeres ( supposed to be a good castle, although we had to skip it due to time constraints), Chartres and / or Versailles on the way back to Paris.

Your plan will work fine. Plenty of time. Barfleur is a nifty place that most people miss. Trouville is fine also. The best places to eat in Barfleur are on the street that runs perpendicular to the port, not the one alongside the port.