Wangerland is a nice Kitespot. In Schillig, when the water comes and goes you can stand for a very long distance. That's optimal for flat water. Schillig is a East coast Kitespot and has a big grass area in front of the kitespot. You can kite 3 hours before and after flood.
In Hooksiel you also can build up your kite in grass or in Sand. And when the water is away because of ebb, you can surf in the priel. :)