Probably stating the obvious but have you tried any travel agents? We found travel counsellors to be excellent for finding exactly what we wanted. No affiliation with them other than having used them for a honeymoon and another big trip a few years ago (before kids). As far as I know they all...
Have stayed on a Sandaya site in Soulac Sur Mer must be 10 years ago. Flew to Bordeaux. The campsite was 3 kms from Soulac. It was nice. You would need a car.