with a family, i think the west coast is a really good pick. if the kids are young then i’d say the vendee as it’s not to far from the ferry ports so not too much of an ordeal for the kids in the car. the weather is usually very predictable, the beaches are endlessly white and sandy. there’s lots of stuff to do withe some decent sized seaside towns if you fancy being grockles. the cuisine is good. lots of moules frites and excellent gallettes.
if the kids are a little older and can stand the journey then venture a little further south to either charente maritime or even further south beyond the gironde. cm has loads to do with some really excellent places like sainte, cognac, ile de re, st savinien. beyond the gironde gives you a beach that runs for half the bay of biscay.
the campsites seem to be really expensive these days. i don’t think there’s much difference price wise between campsites and gites and i’d always choose a gite.
our kids have grown up now and probably wouldn’t want to come away with us again but france has been the destination for most of our summer holidays and they’ve all been fantastic.