Been here a couple of times over the years
http://www.brasilia.fr/uk/
There's an inlet and it's across the other side from Canet Plage with a boat taxi which means you can go over to town for an evening out but it's quiet when you come back.
Right on a big sandy beach, just a 15-20 miles from the Spanish border so it's not crazy like the Riviera
August is pretty crazy anywhere in the South of France so if you can go just before the school holidays that's going to be cheaper and nicer