Can you do justice to visiting Honfleur as a side trip while driving from Rouen to Bayeux in the same day?
Sure. Make it a lunch stop. But don't eat along the port, continue up the street that crosses across the tidal gate and eat where the food is cheaper and better. You can walk the port and duck in the little church in about an hour. Time in the Roudin museum will vary. It's about an hour and a half from Rouen to Bayeux. Cutting up to Honfluer and back won't add another thirty minutes.