Hi Nod
My first suggestion for you would be the Haven (
www.siblu.com )campsites in St Jean de Monts, either Le Bois Dormant or Le Bois Masson. Both are large campsites situated just across the road from each other and you can use the facilities of either.
Haven, in my experience tend to offer the best evening entertainment, and if this is important for you then you need to go to the larger campsites especially as you are going early in the season in June. Smaller campsites tend to be be quiet at night, entertainment-wise early in the season.
The facilities in either of these campsites are first class with indoor / outdoor pools and waterslide complexes.
There are long, very safe beaches within a few minutes drive of the campsites.
Another campsite worth considering is La Garangeoire, a Castels campsite. (
www.camping-la-garangeoire.com) in St Julien des Landes. This has been a favourite of ours down through the years. Its a little bit inland so if frequent trips to the beach is important it probably won't suit. It is however more suited to younger families and again facilities are excellent with its own lake on site.
Another site I would recommend is La Grande Metairie which is in southern Brittany. Again it is a member of the Castels chain (
www.castels.fr ), is very large with indoor / outdoor pool / slides complex and tends to be lively in the evenings even in June. Its also close to the sandy beaches at Carnac. Its only about a two hour drive north from Nantes on a dual carriageway.
You are right to go independent rather than via the operators. You will save money. Use their brochures though as all the best 4 star sites will be in these. If you see a site you like, just Google it and you will find all the info you need regarding accomodation and prices.
Happy holidays
JohnF