Martin , Carnac in one hit is a long run even after a nights rest. We did the Calais crossing and went to Quimper but broke it up into stopping at Chateau Camping Le Colombier in Moyaux ( just south of Liseaux ) Its a Castels site and is ok for a couple of nights . There is an outdoor pool on site and kiddies play area along with a resturant and quaint dovecote which has been transformed into a bar/cum library . The pitches we were on were faily close together and a little lumpy bumpy ( it was an old apple orchard ) and long elec cables required at some + reverse polarity. Staff speak good english but we always like to try our best french . Its basically half way to carnac. Ps you will enjoy the tow over the " Pont de Normandie " bridge , just dont look down.
enjoy your trip. Pip