First, I recommend staying longer than a week in New Zealand. But if that's all the time you've got, just don't sleep.
As for packing, I recommend bringing three bags, actually:
Unless you're spending a lot of time in a small plane with weight restrictions, buy a bag with good wheels, specifically Gregory's new Alpaca wheelie (22-inch, $299; 28-inch, $349; gregorypacks.com), built for expedition travel. The piece that sets this bag apart from other wheelies is the chassis system. It's designed in such a way that the extra-wide handle folds down on either side of the bag, which allows for better stability when you're dodging through the airport. Plus it means that the handle doesn't creep in on your interior space when it's stowed, so the bag feels extra roomy. Added details like a self-locking handle that doesn't rely on a button (so it won't break down) and a hard-core protective TPU-coated ballistic exterior, make this bag bomber. Available in stores in July.
If you plan to bring a camera, carry Timbuk2's Snoop Messenger bag (small, $130; medium, $150; timbuk2.com). This ingenious messenger has a removable and adjustable padded camera insert that will comfortably stash a body, a few lenses, and necessities—all incognito. That may not be such a priority in a safe haven like New Zealand, but if you travel a lot, this is a great bag to have in your quiver. The see-through plastic pouch in the front is a good place to stash small stuff—like flash drives and cards—that would get lost in the two deeper zip pockets. The medium also has a designated laptop sleeve.
If you want to bring home a few special bottles of Marlborough Sauvignon Blanc or merino wool sweaters, stash a ChicoBag Messenger12 rePETe bag ($25, chicobag.com) in your carry-on. This lightweight, scrunchable 80-percent recycled bag (from the ripstop nylon to the key-holding carabiner) stashes inside its own pouch until you need it, has two few secure zipper pockets, a magnetic closure, comes in fantastic colors, and looks sleek and urban.