Is this too much?

That's too much driving for one day.

I think it’s doable if you start really early and don’t expect much time in Dinan and St. Malo.

I see St. Malo eating up more time and energy than anticipated. I was exploring a similar itinerary a while back, and it looked like getting in/out of town and parking was kind of tough. Then, you’re going to want to explore and enjoy the seaside a bit, and this is all after a morning full of driving and a stop in Dinan. That’s all before you get to MSM and deal with that, and hopefully have the energy to explore. I’d be ragged.

You’re not committed or anything so you can play it by ear, but I think cutting St. Malo out makes this way more enjoyable. You’ll have some extra time in Dinan, an easier morning, and a straight drive to MSM with time left to take that on a normal pace.

Of course it's doable. Whether or not it is too much driving depends entirely on how used you are to long distance driving. To us, a drive totalling 6 (ish) hours in a day, plus a meal and brief sightseeing stop, would definitely not be too much. Others might find it too tiring. I assume the reference to crowds was aimed at touring MSM before the biggest crowds arrived in the morning, and then driving to Bayeux.

It is about 3.5 hours from Amboise to Dinan. I would plan for a quick lunch, maybe a crepe, or even something on the go, as you will want to leave Dinan by 2.30 to reach St Malo by 3.15 and have at least 2-3 hours to walk around before heading to the Mont.
I would be inclined towards skipping either Dinan or St Malo.

In planning your time in Dinan and St Malo just remember that you will be arriving at both of those locations during the 'heart' of tourist crowd time of day - making it more time consuming to park, get in and out, and even to just walk around and/or have a nice lunch. I realize that you are timing things so you arrive at MSM in the evening and leaving in the morning to avoid the worst of the day trippers. But realize that both Dinan and St Malo are popular day trip destinations also. Just saying that you need to factor that into your day. The actual time drving from place to place is pretty much what I'm used to on day drives around my state so that would not deter me.

Gigi8,
When you are researching drive times between locations, be aware that most drive-time sites don't figure in time for gas and bathroom stops, and assume you will be on autoroutes (freeways), with toll stations along the way. Also, speed limits are very strictly enforced, with cameras all over. You could get a ticket in the mail a few months after a return home. Be sure to adhere to the speed limit. And add travel time to what you find on the websites. I usually allow for an extra hour on a 3-5 hour drive. (But that is me. Others may differ.)

This one day sounds exhausting to me, and it gives you very little time in Dinan and St. Malo. Allow yourself three hours (including time for lunch) to explore one of these two. I would drop one of them if you want to get to Mont St. Michel in time for a peaceful sunset dinner, needed after a long day in the car. Sunset from the Mont is regularly praised on this forum, so lucky you to be able to see it!

My guess is that you are referring to the crowds arriving at the Mont, not at Bayeux. Yes, being there in the early AM will give you the advantage of missing the worst crowding. That will begin about 11:00. How many nights will you spend in Bayeux? If you get there early enough in the afternoon, you can visit the cathedral and the tapestry museum that day, saving the next full day for the DDay landing sights, museums and cemeteries.

Whatever you decide, keep in mind that your drive times may be longer than planned. If they turn out not to be, then great! If they are longer, you are prepared.

Bon voyage et bonne chance!

You can also think about visiting Le Mans, Vitré and / or Fougères on the way to Mont Saint-Michel. Unless they are real mustsees for you, consider skipping St-Malo and Dinan. The historic center of Le Mans is certainly worth a visit and the time left can be spend in Vitré or Fougères before driving further. You can decide that on the spot if you like. Think a more relaxed way arriving in Mont Saint-Michel in the evening. Sunset there is not to miss btw.

As usual, y’all did not disappoint! Yes, I was referring to having a few hours in the morning in MSM before the day crowds arrive, and then we can head to Bayeux. I think you have convinced me - we need to drop St. Malo and just enjoy our time in Dinan. Thank you for your input! I will probably have more questions as we plan!

Gigi18,
When in Normandy, at the beach sites, if you can, be at the Amnerican ceremony for the flag lowering ceremony at the end of the day. It is very moving. Info on that and other American sites all over the world is at abmc.gov, American Battle Monuments Commission. I found it helpful when in France and Belgium.

Oops! I meant be at the American cemetery for the ceremony! Sorry for the typo. Hope I clarified my post.

Ha Judy! I didn’t even notice the typo! Funny how one’s brain just adapts!