We stayed at Domaine de Kerlann in Brittany and it was idyllic. Great pool, indoor with childrens and baby changing tables, family changing rooms etc. splash zone, lots of playgrounds for different aged children. Lots of places to go nearby, Concarneau, Quimper, Rospico beach which was empty and amazing, lots of beautiful little picnic areas, truly lovely.
We then went to Le Bois Dormant and it was terrible, pools were dirty and cold, no decent changing areas for the baby, generally unkept, Vendee has much less to do if the weather isn't so good, but lots of beaches if the weather is great. Plus it's a longer drive. Also, the caravan we were in was owned by someone else and let to Siblu, the owner actually didn't realise it was let to Siblu that week and walked in on us at 2am turning all the lights on and shouting in French. We panicked because it was the same time as the Madeline McCann thing and our DD was that age. It was horrible. Siblu moved us, or let us move ourselves but it was a pretty horrible time as we never felt safe there again. The staff weren't particularly good, very snooty. However, chances are something like that is pretty rare and if the weather was good there (it rained for our fortnight in late May) it would have been a better holiday.
I do definitely recommend Domaine de Kerlann though - we'll definitely go back there.