First 2 weeks of September is my favorite time to get there : always windy, just after tourists, just before duck hunting (which can limit access to lagunas last 2 weeks of September), peak of water temperature.
The number of spots is unlimited! So get there and ask the locals. With any wind directions you can have flat session in shallow water lagunas or a descent wave session.
''Kite aux iles'' on Facebook
Ask for Lionel, he knows this place inside out!
PS I second the other comments. I'll be there the first two weeks of September.