Stayed here last summer – its in the west.
http://www.campingporsperon.com
Nice site, well run, no pool, close to a beach but this is less child friendly than it looks – shelves a bit. Nice coastal paths. We drove to a large beach at the end of the the peninsula called Bay de Trespass – next to Pointe de Raz. You would probably not want to camp here as its quite exposed but the beach is fantastic for swimming, boarding plus has life guards. Decent cycling from the site either along the coastal path (cheeky and challenging) or around the peninsula (with some singletrack).
That said the weather was indifferent – this would be the same at Quimper and Carnac. It was great when he sun came out and things warmed up but the cloudy drizzle eventually gave way to full on downpour so we drove a few hundred miles up the Loire valley in order to escape and dry out the canvas.
This year we are going further south in search of a better climate.