Rich, if there are specific museums you're interested in (WW II in Bayeux, the tapestry in Bayeux, Peace Museum in Caen, Airborne Museum in St-Mere-Eglise, etc.), you'll probably find a list of the days they are closed on their websites. My guess is that there will be D-Day tours running, though I suppose they might be sold out by now.
If the news turns out to be bad, there are quite a few attractive costal towns east of Caen. I enjoyed just walking around Cabourg, Deauville and Honfleur. Unfortunately, only Deauville/Trouville has rail service, and I am afraid there won't be a lot of buses running. But Deauville and Bayeux itself would probably keep you busy for about a day if you enjoy just wandering.
I recommend taking a D-Day tour in any case. That will be a lot more illuminating than the do-it-yourself approach.