try Les Grands Pins camping at Lacanau Ocean - superb surf area, very friendly campsite, cheaper out of peak season, good quiet beaches to N&S - go to Arcachon and surf the Grand Dune du Pyla - the biggest sand dune in Europe - take an old bodyboard!!
Can only agree with this. Fantastic campsite for kids, try and go as late as possible. Lacanau is so much more chilled than the spots furter south (Hossegor for example) and if you get some bad weather, you're only an hour from Bordeaux which is a sweet city. Take the RN from St.Malo which runs down parallel to the motorway and enjoy the rolling miles of avenues, vineyards and lavender fields. Way jealous!