It's a nice site - we were there about 4yrs ago I think. Here is their website in English. It's run by Yelloh, who are a well-known camping group.
There was a small but adequate supermarket on the main road into Carantec, at the turning to the campsite.
Launderette on site - buy tokens at reception.
Take old flip-flops or crocs for everyone to leave at the swimming pool entrance.
I seem to recall a lot of German-style sunbed bagging going on, as the pool is open to adults only early in the morning. I would nip in while the DC were at the kids club (v.good) and drape a few towels in your favoured area 
Beach by the site is ok for a stroll or stream damming, but quite tidal so not good for beach activities. The main beaches in Carantec are beautiful (think Cornwall with sunshine). At low tide you can walk across to one of the islands.
The nearest town, Morlaix, has a good market. Park and walk in along the river and watch the boats.
Route planning via michelin is the best site. Fairly straightforward drive IIRC.
Quite
actually as it's somewhere I would definitely go back to. Have a lovely holiday.