Atlantic Coast.
http://www.velodyssey.com/
Every year we tour with our 2, and last year we decided to stay in our home country and do the Atlantic Coast ‘ Les Landes’ after having had 2 years in Denmark.
We biked from Bassin d’Arcachon down to Biarritz last summer. Through the pin e forests on pristine ribbons of cyclepath tarmac mostly away from roads. A 3 week camping trip with Etienne 7 on his bike and Pia 4 on her bike and follow-me tandem. Then get the train back (well ok we started at Parentis, down to Biarritz, train up to Arcanchon then rode down to Parentis were we found a campsite that would let us park our car for 3 weeks).
Be warned: In summer the campsites are very busy, sometimes expensive and sometimes very noisy. If you don’t mind the lack of options (i.e. you either head north or south every day) then it has much to reccomend, especially if you have not been there before.
I commented on a thread about the area about a month or so ago.