June/July is middle of winter in NZ. So plan for cold, wet, windy weather. Winter in NZ isn't especially harsh - in Auckland you'll get a few frosty mornings where the temperature approaches 0 degrees C - but no snow.
It depends what you want to do while you're here. I recommend Queenstown (South Island). The scenery is simply stunning, and there are a million mad ways to entertain yourself. Most involve strapping a rubber cord to your feet and leaping off something, or being strapped into something else and travelling at unsafe speeds along rivers, through the sky, underground...
Milford Sound is also very beautiful while you're in that area.
In the North Island Rotorua is worth a look (thermal park). Further north there are beaches everywhere. On the West coast (Tasman sea) they tend to be dramatic, with dark sand. On the East coast (Pacific ocean) they tend to be more stately with white sand. You probably wont want to go swimming in the middle of winter but they're still fantastic to stroll along.
AndyRage's mantra for graphics engine code:
"Sure - how hard can it be?"