Hi Andy,I didn't think you could take a caravan onto an Aire? We stayed at the municipal camp site in Epernay (South of Rheims) last year. Showers not great but other than that quite nice. You can book. They run tours out to champagne houses which (from memory, too much tasting, forgot to spit it out!) were great.
We used Municipal sites extensively when travelling to our booked locations. One advantage being that being municipal many would be near to shops, restaurants or bars.After travelling around France, every 12 weeks for 4 weeks at a time, for 5 years. I wouldn't stay in an Aire overnight, there are plenty of municiple sites, all over. The CMHC book of sites, for France is very good, all sites, municiple, Farm private etc. with contact numbers and opening dates.