Sharon,
North Brittany is generally a rocky, dramatic coast with fantastic sandy bays. One good example for a campsite is "Camping les Capucines" www.lescapucines.fr
South Brittany is generally flat and sandy with some long beaches.
One good example for a campsite is "L'Orangerie de Lanniron" www.lanniron.com
To get a flavour of the place, you may want to have one week on the North and a second on the South coast? But there are so many good campsites in Brittany you may want to get a copy of the Alan Rogers guide and a copy of Site & Paysages freebie www.sites-et-paysages.com/gb.html
Robert