It's a lovely site, really family friendly and the pool area is brilliant. The indoor pool was newly built when I worked there and a godsend in bad weather. The whole site is beautifully maintained and the owner, Monsieur Bellec, is obsessive about gardening and litter. If you see an old guy on a ride on mower around everywhere that's the owner!
If you plan to cook then I would go out of Carantec into St Pol de Leon to the big Super U, the nearby Casino isn't great. There are lovely bakeries and patisseries in Carantec though. The best one is as you walk into town from the site, I can't remember what its called but it has a green canopy and they do the most amazing Breton Gateaux and a baguette with cheese and chorizo in it
A few lovely restaurants and Creperies in town and by the beach too, they all do good value set menus. My favourite is L'abri de Pecheur which is down by the port road, but Table de Ty Pot in town is lovely too. And you must go to the Creperie by the church!
Carantec isn't really touristy but is all the better for it imo, it's lovely. Lot's of property porn if you walk along the coast road. If you like walking you can pick up a route map for a walk around the coastal path and the Il de Batz which is about 8k - it's a great walk.
Nearby must visits are the market in St. Pol and Morlaix - iirc its on a wednesday where they have street theatre and music on.
Sorry I've written a bit of an essay! 
I really love the area, it's one of my favourite places in the world!