I was in Naxos June (I think

) last year.... there definately is kiteboarding there... along with a kiteboarding school. There are a few beaches where you can kite and unlike alot of Greek islands Naxos has sandy beaches.
The kiteboarding school provides a service where they can take you to the kite beaches and provide boat support for 70 euro if memory serves me correctly.
I believe there is a website for the kiteboarding school.. of if you like I can try and dig up a brochure that I took while I was there.