Heard of Several [b:33zlgzfy]BIG[/b:33zlgzfy] Snapper being caught in the shallows in the Kenepuru. For spots try a quick search, it has been discussed several times before and I am not experienced enough at Snapper fishing to pick one over another.
Personally I would go to either French pass or Kenepuru. According to my fish finder the QC is still relatively cold (around 14). The warmest water (just below 17) is in Port Underwood, Cloudy and Clifford Bay. The outer sounds around to the Mouth of the Pelerous is also warm. Tasman bay and the western side of the sounds is just below 16.
Port Underwood would be a gamblers choice.