It's a Camping Cheque site - and the CC website suggests that all but the restaurant will be open. Usually they indicate with opening/closing dates if things are not open.
HOWEVER I would definitely check with the site itself before you go! There'd be nothing worse than arriving on site to find only one toilet and shower in the block open - and the pool full of green slime and frogs from last season!
I'd email them and ask. Even relying on information from a previous year can be tricky! We were at a site in Port Camargue which promised all services open, as indeed they usually were - but not the year we were there!