Usually I can do itineraries in my sleep but for some reason I can't seem to concentrate on this one. We'll be going to the DDay beaches, Bayeaux, and Mont St. Michel. We'd also like to take a couple of days and relax on Jersey. This will be the middle part of our trip which starts with about 4 days on the Rhine/Mosel and ends with 4 days in Paris and those plans are set. This leaves us with 4-6 days for the coast. We plan on going in October but haven't bought tickets yet so we're flexible. We will also be traveling by public transportation. We had thought about staying in Bayeaux but any help with the best town to base ourselves in as well as traveling to Jersey is appreciated.
Condor Ferries runs boats between St. Malo and the Channel Islands. I think there is a bus between Mont-St Michel and St. Malo in the summer--check Rick's book for details. St. Malo is a charming town, so you might want to stay there and do a day trip to Jersey instead.
A year or two ago we did a trip with some of your highlights, basing our travels in Bayeux at Hotel D'Argouges which we liked VERY much & I cannot tell you how very neat the Bayeux Tapestry Museum is. We devoted one day to Bayeux + recovering from jet lag after intensive travel to see things that were on a bucket list - D-Day + Mont St Michel. In one day we did the D-Day Beaches + Ste Mere Eglise, dining at the restaurant named for the American Paratrooper John Steele (which sounded like it would be touristy & bad but was in fact very good). That is easily one full day out of Bayeux - as is Mont St Michel which we combined with Dinan (a very long day). It was after those two intensive days that we spent time in Bayeux & saw the tapestry museum & the town, & we were glad of the rest in the evening on that 3rd day.
Note that you can do the D-Day beaches on your own, or with an intensive guide. We did it on our own & felt that with reading in advance it was fine - but the beaches are not confined to the burial grounds & you will want to see Pointe du Hoc which was to me at least as moving as the cemetery. Mont St Michel is something of an athletic event as you park & WALK & WALK & then you get to the Island & you WALK straight up to the church at the top & then you WALK & WALK back to your car. This is how things were 3 years ago & perhaps the process has changed (my kingdom for a bus!). What I am saying is that this is not a trip you can knock off in a couple of hours - it will take a well-planned morning to get in & out & you would be pressed to do it as we did with a trip to Dinan included to enjoy oysters.
I do not encourage you to go to Jersey overnight as part of this trip as when you consider the ground you already contemplate you will be crazy exhausted. Consider instead going to Rouens perhaps or driving through the Normandy countryside. There is much to see & do & you will love every moment.