Ferg,
I haven't been to New Zealand, but I know a few people who have. The footage coming back from there is pretty incredible. If you're a proficient kitesurfer, snowkiting should be easy to pick up. Nevertheless, it's prudent to start out on a smaller kite. An alternative would be to start in lighter winds with your 12 m. I fly foils on snow, so I can't give you too much advice on how to fly your LEIs. "How to Snowkite" from
http://www.snowkitefilms.com has tons of good information about LEIs on snow. I highly encourage you to buy it, because $40 spent on the video is better than $400 spent on hospital bills and equipment repair. Have fun with the Kiwis.
-Eric