Normandy, Loire

The obvious omission to me is Bayeux. The old town is picturesque but you have an opportunity to see others, so certainly not essential. But the cathedral and the tapestry are worthwhile even if the historic architecture doesn't especially interest you. There's also a small lace-making display.

But I haven't been to Avranches and know nothing of its attractions.

Edited to add:

The usual advice here is to see Mont-St-Michel late in the day or very early in the morning after spending the night nearby. I haven't been there, but I've read nothing that makes me think it's a full-day destination, even aside from the fact that it's reportedly miserably crowded during day-tripping hours.

There are two towns I enjoyed a lot located south of Mont-St-Michel: Vitre and Fougeres. Fougeres is right near the shortest driving route to Amboise proposed by ViaMichelin.com. If you have time to see one or both in transit, I don't think you'll be disappointed. They are not tiny villages, though.

Thank you so much. I am definitely will look this two up and try to cover them on the way to Amboise.
We only pick Avranches as a stop because it looks like its on the way from Honfleur to St Michelle ( only 25 min from there). I don’t have to spend hole day there just want to get there in the morning.
Any suggestions what to see on the way from Rouen to Avranches?

I've done much of what you outline here, at the same time of year. My concern is you've given yourself only two nights to "explore" the Loire, and then just part of a day to see Versailles en route back to Paris. Distances between the Loire Valley chateaux are great. If you're satisfied with just seeing the ones nearest to Amboise, you will probably be able to visit three of them and do justice. Be sure to map out which ones are your top priorities, though, because if any are not within the easy Amboise orbit then you may only be able to visit one per day.

Driving in Amboise is pretty unpleasant, too -- personally I'd choose a different base since you will have a car.

Similarly, leaving Amboise (or elsewhere in that vicinity) and stopping to visit Versailles means you'll need to get a very early start. The distance is not all that short, and once you leave Versailles you're likely to encounter traffic heading into Paris.

I would definitely sleep near the airport the night before the flight; if at all possible, turn in the car and use an airport shuttle in the morning. There can be delays turning in rental cars if by chance the computers are down and/or lots of other people are returning their cars at the same time as you.

Do not try to drive from the Loire to CDG for an early morning flight. I can't even imagine how stressful that would be. If you look at a map, you'll see that CDG is all the way around the other side of Paris. It would be like leaving from Cape May (NJ) in the morning to drive to JFK for an early morning flight.

Thank you ! I actually already booked hotel in the airport!
Versailles is not a must , it is more a suggestion.
We may just stay in Loire for that last day. What would you pick as a base if we planing to visit Chenonceau, Cheverny , chambord and Vilandry . Can you advise any wineries around those Château which can be visited on the way

I'd push on to MSM on Day 6 and spend that night there. That will give you the best hours there, and an early start towards the Loire.

If that feels like too much driving for one day, consider spending the night of Day 5 in Honfleur, very pretty town. But I don't think you have to do that.

Why do you want to get to Avranches in the morning if you don’t know anything about it? It’s a big jump, if not as miserable as MSM to Amboise. You clearly love to drive.

I’ll bet Avranches has good oysters. But Fougeres and Vitre are more historic. Alas, St Malo is beyond MSM, but somebody might ask you if you went there. Somebody who reads Rick Steves might ask you if you went to Dinan, but I like Fougeres and Vitre better. (accent marks omitted)

I don’t think MSM requires more than 4 hours, especially with 5,000 of your closest personal friends joining you.

I guess I wasn’t clear enough in my description. I was planing to get to Avranches late night , use it as a sleepover stop to get MSM in the morning be done there and be on the road to Amboise.
But Adam above suggested to go to MSM straight from Rouen on day 6 then sleep in Avranches and have an extra day in Loire. Might be not a bad idea.
What town you would suggest instead of Avranches in close proximity to MSM

Adam , thank you . I like your idea . Honfleur sounds tempting for nite stop so is Etretat but I am trying to avoid too many one night stops so if you would choose which one of three you would pick for the two nights stop considering that I am driving from Paris: Rouen, Etretat, Hunfleur?

It takes a good bit of time to walk around the historic (rebuilt) center of Rouen. It isn't exactly small.

I recently returned from the first half of your trip and must say you are missing the incredible story of D-Day. It is perhaps the most moving trip I have taken. That aside, we rented a car at Mantes La Jolie, to avoid Paris trip and headed to Giverny, wonderful and absolutely a good choice. Walk up the hill and have lunch in a quiet outdoor cafe, away from the crowds. The earlier you arrive the better.
On to Rouen, which we both did not care for. Perhaps we were cathedral tired, and somedays in travel are just like that. We viewed it as a shopping mecca. We drove the coast seeing Fecamp, Entreat, nite in Honfluer on to Deauville, Trouville and 4 nites in Bayeaux. You do not need a full day in Entreat, I would head to Bayeux for the night if possible. If not, I would include Bayeux on your way to MSM and spend the night there if possible. The Bayeux tapestry was most interesting. The manner in which you view it, headphones telling the story as you walk through viewing it (maybe 15 mins) in silence. We were there at 9 and had no wait. The museum attached require another hour.
MSM does not require a day and the only way to beat the crowd is to spend the night. The abbey is fascinating, but the crowds are overwhelming.
Also, there is the Peace Museum in Caen which was quite incredible, we would like to return as it was very time consuming to see it all. We get a little overwhelmed after 2 hours.
Good luck

Agree with Ellen and would add that the American Cemetery is the one thing you should do even if you skip all the rest of the D-Day spots.

Thank you Ellen. What time in your opinion is bette to visit MSMs: morning or night?