We've been twice with Keycamp, once to Les Biches, St Hilaire-de-Riez in the Vendee, and this year to Domaine de la Noguiere, on the Cote D'Azur.
We had a great time at both sites - the Vendee one was more set up for English families as la Noguiere is new to Keycamp this year and is a Dutch run site.
Both had great pools, which the boys loved, though the weather wasn't great in the Vendee last year, so we weren't able to make as much use of the pool as we did this year.
As mine are older, I can't really comment on the activities for smaller children, but mine had a great time. No2 really enjoyed going scuba diving in the Med (a trip organised by the site) - as did I - it was a wonderful experience for both of us.
I thought that the accomodation is good, though a bit cramped for a family with older children if the weather is poor and you end up spending more time in the van. This year we had wonderful weather and decking outside the van - which effectively doubled the living space.
We liked it so much that we'll be booking again for next year.