Max,
We've used some of the sites that are part of the "Sites & Paysages de France", and these in the Loire:
Chateau des Marais, Muides - about 10km North of Blois - this site is within 1km of the Chateau de Chambord (take your bicycles or rent) and within an easy drive of many other famous chateaux.
Chantepie, Saumur - use up some of the extra payload to buy a case of Saumur Champigny - a stunning red wine that will be great at Christmas
La Citadelle, Loches - easy walking distance of the town.
Our only rider is that we visit in June, outside school holidays, and even then these sites are moderatley full - upto 50% static tents of the Eurocamp type - and it's starting to get really hot.
Robert