Never kited there, but grew up there and I think the main spot would be at Wharewaka point with a southerly - south westerly, launching on the second outcrop from the very point (center of this map
http://goo.gl/maps/lZsPn). This area is also the most used by pole dancers, but it is also quite popular for dog walkers, families and boats also launch near by. Here's the windsurfing spots which might help
http://www.winzurf.co.nz/windsurf/wgtnz/wgtnz21.htm . The Lakefront could be an option if it is empty but don't count on that.