Hi
We are also fans of this area. As others have said, excellent for walking, cycling, canoeing (available for hire in many places), bird watching - and just enjoying France. It is probably best to stay within the area as access is not the fastest from elsewhere. We think the most attractive part is the area between Coulon and Maillezais. Coulon is a very attractive canalside village.
Re campsites, we have stayed at Camping Le Relais du Pecheur at Le Mazeau. This is a small Camping Municipal in a quiet location close to a canal, just outside the village. It has hedged pitches; the facilities are OK, but a little dated. There is a 'location' for canoe and punt hire closeby. When we last stayed there (21011) we felt it needed a bit more TLC, but I see it is in the latest Caravan Club Europe Guide with a more recent entry (page 270). We have also stayed at Camping Les Conches at Damvix. This is a fairly large, pleasant campsite just outside this canal-side village. It has good sized pitches and a small swimming pool. It was not crowded when we visitied, but this was towards the end of the season. However, do beware of the access slope to the site, as there is a danger of grounding a long outfit.
The whole area is well worth a visit. It is quite well described in a guide 'The Vendee and surrounding area' by Angela Bird.
Bonnes vacances et bonne retrait.
Cheers
Paul R T