We were there 3 years ago and loved it. There in summer and not too mad, it's a big site. That year the entertainment was amazing - theatre company doing musicals - free and top class but obviously don't know if they still do that. Perpignan good for a day out.
Again, we went a few years back one August and loved it too - agree that the entertainment was amazing. It was busy, and you had to get to the entertainment early if you wanted a seat, but it wasn't tacky or overcrowded and our kids had a blast.
You have to drive to the beach though (We now choose sites where the beach is walkable)
We stayed closer to the beach at Camping la Bois du Valmarie and visited la serene as friends stated there. We all far preferred Bois du Valmarie - la sureness was too Brits abroad, too busy and expensive! Only diwn sued to Karen Valmarie was that it us hilly but you get amazing views of the sea and Pyrenees from the pool area. Also you are closer to walk into marina etc fir meals and drinks (and tat market) at night.