Both the above sites are Camping Cheque sites - and start accepting them again about the third week in August. We've stayed, several times, on both. Champs Blancs will give you a pitch with private bathroom, in with the price of your Camping Cheque - which is really nice, but the cabin can intrude on some of the space on the pitch, and depending on your outfit you may not have room for an awning. We bought a pergola the first time we were there because it was so hot and we needed some extra shade but our standard caravan awning wouldn't fit.
On the way back to Clermont Ferrand worth a detour is the Gorges du Tarn area - Les Peupliers is another Camping Cheque site there - just for the stunning views, and the wildlife. You'll get to go over the Millau viaduct too whilst in that area.
Both these areas are places we've been back to many times in the past so if I can help at all just post again.