Rouen

I've not eaten there but La Couronne in Rouen was apparently where Julia Child had her epiphany about good food.

"Child repeatedly recalled her first meal in Rouen as a culinary revelation; once, she described the meal of oysters, sole meunière, and fine wine to The New York Times as "an opening up of the soul and spirit for me."" (from the Wiki article)

It sounds like you will have a car so when you are doing the WWII sights, I'd add in Pegasus Bridge when you are in the Arromanches area. It is very interesting - doesn't take long to see where the gliders landed but to me it was shocking to see how accurate they were in getting close to the bridge.

If you watch The Longest Day film they re-enact the glider scene and this is also where Lord Lovat and his bagpiper stride up to relieve the defenders. Very stirring and just amazing to see this actual area.

I had a great seafood dinner at La Pêcherie in Rouen this March. Not too pricey, and very recommended.

Worth to visit upstream along the Seine is Château Gaillard for the view and nearby Les Andelys.
Downstream along the D982 the abbeys of Saint-Martin-de-Boscherville, Jumiège and Saint-Wandrille, the latter still having a living community. From there following the “Route des chaumières” (cottages) to Vieux-Port and Marais Vernier on the way to Honfleur.

East of Rouen and north of Andelys worth the drive Lyons-la-Forêt.

Thank you all for the good suggestions. They are in my trip notes!

I'd suggest adding Etretat and Fecamp to your things to see. There are spectacular white cliffs (look like Dover). The beaches are pebbles. Etretat is built more for tourist trade but both are worth a visit. If you're going to see WWII things. The cliffs above both are dotted with German emplacements that were abandoned, rather than destroyed, after D-Day. They are still intact but mostly filled with dirt. I started by going to the church on the hill, visible to the north, above Fecamp, parked there and walked to the cliff. Then walked the trail along the cliff. Etretat has similar (church, cliff, trail, emplacements) but gets considerably more tourist walking traffic. Etretat's cliffs have some features that are a little more picturesque.

Le Havre (pronounce lou ahve) is a surprisingly nice city with beaches (more sandy than most of the area).

You probably already have Honfleur on your list. I skipped it because I was planning to see similar towns in Brittany that I presumed would be less crowded.