Corsica campsites

Dear all, I'm new to the club..

I have booked some ferries to take the children to Corsica during the second half of August. The main purpose is to water proof the kids by doing some snorkeling and other water activities. Our van is nearly self sufficient and we're easy going so the main thing we're after is a shower and a nice coat line. 

Does anyone have recent experiences with Corsica?

Is it necessary to book a campsite there or could we just drive around and find one during the high season? 

Any recommendations for good sites? We're landing north...

Thank you very much. 

Kind regards

Otto