I have been to seven D-day anniversaries, including the 70th and 75th. I will also be returning for the 80th, and have been there other trips and times. I personally think the dire warnings of crowds are overblown, but it does take some planning. It will be crowded, but it is a very large area with much to see and do. There will always be some event to attend—even on the anniversaries. I presume you already have accommodations. If not, it is already too late (sorry). I also presume you will have a car, otherwise you will be restricted to a very small area around Bayeux. Great city, but so much will happen in many other areas and there isn't workable public transportation in that region. Also, I can't tell if you are interested in U.S. events, British or Canadian. But Bayeux was not an area of U.S. operations in the Battle of Normandy. If both lodging and transportation are already secured,...
Many of the festivities will happen the week of June 1st–9th and many of the events, celebrations and memorials are not even listed yet. And they won't be until this Spring. Of course there are many events on the 6th itself, but the events happen over a much longer time period. Plus, the transportation restrictions will be on the 6th itself.
Yes, you could go to Mont-Saint-Michel as a day trip, but with only three days in Normandy I wouldn't bother. MSM is best as an overnight anyway (crushing crowds mid-day) and there will be much to do in upper Normandy that week. If you had your heart set on the Mont, you may consider going on the 6th itself. I may even do that this year but haven't decided. If you could extend your trip a little, there will be a mass parachute drop on the farmlands inland from, and in sight of MSM on June 7th organized by the Round Canopy Parachute Team (RCPT, a French WWII reenactment group). If you will be in Bayeux on the 6th, consider applying for a free ticket to the ceremony at the Normandy American Cemetery. This is the only way to visit there on that date, and the two times I have filled out a form (https://www.abmc.gov/), I received notice while in Normandy that my application was approved. It is a very moving ceremony, and will likely be attended by Macron and Biden (or whoever the U.S. President is at the time). But it will take the better part of the day between the ceremonies, getting there and back, plus security (you have to take a government provided bus from a nearby village, you can't make your own way to the cemetery on the 6th itself).
One site that will list a lot of ceremonies on the Cotentin Penninsula is:
https://www.ot-baieducotentin.fr/en/
But don't expect to see much listed before April or May. The Cotentin is the epicenter of American operations during the anniversary, as that is where the U.S. military is based during their stay there, and was the location in 1944 of the U.S. Airborne drops. Sainte-Mère-Église is a party town all week long, culminating in a mass parachute drop by many different military and reenactment jumpers at the La Fière Causeway on June 9th. There will be fireworks all along the coast on the 6th itself, including on Utah Beach.
Another site that may have events listed is:
https://en.normandie-tourisme.fr/
If you have any questions, please feel free to send me a message.
EDIT TO ADD: A more direct link to the ceremony at the Normandy American Cemetery is here:
https://www.abmc.gov/d-day80
Note that they will not be open to the public at all on June 5th next year.