As a bit of a veteran I would suggest Britanny, especially the Southern coast. Ferry to Caen, Roscoff or St Malo, and treat the journey as part of the adventure for the kids. Look at Camping Life brochures. All the sites are kid friendly, all have pool, play areas, and all are fantastic fun. I always took the bikes. Google Ty Nydan for a site with some adventure stuff for the kids, and a great Cidrerie next door!!! Otherwise, go independent to save a bit of commission, and if you like it upmarket (although very few people who go to such sites are hard to holiday with) try Les Castels sites. Other great sites are the Grand Metrerie (on site petting zoo and goats) , Fousenant La Foret, superb secluded cove beaches and loads of local bird life, Carnac, (standing stones and wild beaches) Quimper (coastal history to die for) Benodet are towns to visit and all have loads of campsites nearby.