Stop by Dunedin and see Baldwin Street. There is also a penguin reserve there where you basically walk through trenches into little "pillboxes" and are able to see them in their natural habitat. Its amazing. Lots of awesome scenic areas which are easy to get to.
On the off chance you end up in Wellington, stop by the "Museum of New Zealand (Te Papa Tongarewa)". Some of the exhibits are incredible, incluyding the WW1 exhibit on Gallipoli, which was one of the most incredible and moving war exhibits I have ever seen.
And if you're a drinked and enjoy Jim Beam and Coke, or Canadian Club and Seven Up, they have them in cans pre-mixed to 4.5%. I would HIGHLY recommend the pear cider.