I assume you mean late April of next year.
Overlord Tours has in the past offered a full-day tour originating at the Bayeux train station that is timed to the arrival of the first morning train from Paris. The website indicates this tour runs only on weekdays, but I wouldn't assume it runs every weekday, especially in April, so you'd need to contact the company. It would be safest if you could be available on several days of your stay in Paris.
Overlord Tours use minivans; they aren't big-bus tours. I think you'd end up with more actual touring time in Normandy by taking the train to Bayeux rather than trying to find a bus tour all the way from Paris. However, you need to be realistic about what can be accomplished on a day when you're going to need to spend nearly 5 hours traveling back and forth on a train. I doubt that you'll have much if any museum time. The invasion sites are quite spread out, and they aren't right at Bayeux, either. The tours--no doubt responding to what their customers want--focus on the invasion sites rather than the museums. Quite a few of the museums are accessible by public transportation, whereas it's harder to get to the sites along the beaches.