Carnac is a great spot for a family holiday. Lovely beach and nice town to stroll around.
La trinite ( about 3 miles away) is a lovely yachting town.
Drive down the Quiberon Peninsula alond La Cote Sauvage for a nice day out.
A little bit further a field Auray is beautiful, but make sure you walk down from the new town to the old harbour or you'll miss the best bit.
Vannes is a larger walled town but very pretty and great shopping.
Josselin ( maybe 30 miles inland) has a beautiful medieval chateau.
These are all I can remember as it's about 10 years since I was there, but Brittany if one of my favourite parts of France & I hope you enjoy it as much as we did!
(We stayed at La Grande Mertrairie camp site & another site in La Trinite another year as we had a touring caravan at the time.)