In September the weather can be excellent and not too hot, so good for travelling around. I have travelled the region north and the Seine just west of Rouen the last week of last September and the weather was a bit more chilly, but with enough sunshine for me really good. Sorry if I am repeating idea's already mentioned in other posts, but this would be my plan.
What you can do in day 1 depends much the time your plane will arrive. If it is in the morning there is enough time to visit (nevertheless your last post) Giverny in the afternoon and having the oppertunity to deal with jet lag. Giverny is 100km from CDG and most take Paris for driving the A13 toll road to Giverny and Normandy. To avoid busy Paris you can go directly to the N104 just north of CDG with direction Cergy-Pontoisse. Follow the A15 to Magny-en-Vexin and drive from there through lovely countryside, Ambleville and La Roche-Guyon to Giverny. This route is about the same length and way more relaxing. Stay in the neighbourhood.
If having time and interest you can make a little detour to Auvers-sur-Oise just north of Cergy-Pontoisse where Vincent van Gogh spended the last period of his life.
Day 2 You have the whole day for driving to Bayeux, together with a visit to Honfleur and Deauville. The coastal route between the two places has some nice spots and views, to see a really lovely Normandy style village and countryside make a detour to Beuvron-en-Auge east of Caen.
Day 3 Whole day for visiting the D-day beaches, at the end of the day you can drive to Le Mont-Saint-Michel. Last year early June I arrived at 9pm and had the feeling having the place most for myself. Later it became a bit more busy as many want to see it illuminated in the dark.
Day 4 Visit MSM again before the crowds arrive or/and drive along the coastal road to St. Malo with a stop in Cancale. A few hours is enough to see St. Malo and have enough time to visit Dinan in the late afternoon (for having dinner) too. You can stay in Dinan or go back to the same hotel/B&B near or in MSM.
Day 5 Drive to Amboise, you don’t have to visit the castle there, it is nice enough to relax and walk around a bit.
Day 6 Not too far away from Amboise is Chenonceau, think the most beautiful of all in the Loire. Best is to drive this day back to CDG for a hotel as close as possible for the flight back home. Worth is a detour to Chambord just for seeing the outside and it’s dramatic setting. Late in the evening you can visit Paris. Worth is looking for a flight back home from Orly as you can avoid the busy traffic or plan to drive around Paris after rush hour.
Day 7 Depending the time you fly back home. If you stay near CDG and if having time you can visit Senlis and also nearby Château de Chantilly.
Rouen is certainly worth a visit but not so easy to drive through. Downstream of Rouen you have a bunch of lovely villages (as Judy already noticed) but you need time as driving around is very time consuming. But if you like a stop in La Bouille along the Seine and just a few minutes drive from the A13 is worth to consider.
It is a tight schedule, but now you have an overview if it is doable for you or not. With such a tight schedule book the hotels/B&B’s in advance.