Yup, travel light.
If need be, once you get to Christchurch, take your extra stuff and send it guardmail. To do it bring it to the APO post office and they’ll walk you through. The post office is in the same complex where you get the clothing and is easy to find.
Zondra is right, Once you fly down, wear all the heavy stuff, or put it in the carryon. Make sure you can squeeze the carry on into the box. They will sometimes not allow you on if it’s too big. If you have to get creative. put your bag in first and squeeze your stuff in any empty place.