Golf du Medoc in Bordeaux, hosted French Open - hotel on site if needed, although only 30 minutes from city centre. Two great heathland courses and some decent vineyards close by.
The obvious option is Le Touquet and Hardelot. Both have two courses, whilst "by the sea" neither La Mer or the Dunes are links courses. Le Touquet is quite decent for restaurants, Hardelot has a decent straight of restaurants near the beach too. Both locations allow you to mix and match between them, additionally you could add Belle Dune or Wimeraux as additional courses to play. We went last year and played Hardelot Dunes, Belle Dune and La Mer. It was a good trip and all courses were good, just make sure they're not doing maintenance during your trip.