We just stayed in Bayeux for three nights in late November. There are definitely pros and cons to off-season travel.
Pros: We toured Arromanches, Omaha Beach and the Overlord Museum on a cold and rainy day. We saw only one other family (other crazy Americans!) on Omaha beach. There were only 2-3 other groups at any of these sights: the 360 cinema in Arromanches, the Overlord Museum, the Airborne museum in St. Mere Eglise and the Utah Beach museum. There is very little traffic. We don’t worry about finding parking anywhere!
Now for the cons - almost ALL the restaurants are closed for the season. We couldn’t find a single restaurant open anywhere near Omaha or Utah beaches. We stopped in a boulangerie and asked. We were told they ALL close in September for the season. Thankfully this boulangerie had a nice selection for a picnic in the car. Almost every restaurant has a website, but they don’t show they’re closed. So be prepared and pack your picnic when touring the beaches!
The same goes for shops In the villages near the beaches. Get your souvenirs in the museum gift shops - there aren’t a lot of other shops open.
Now, I’ll take this over crowds in the heat anyday! But in case your planning an of season trip, be warned that your choices are much more limited!