Hey There
Hope you enjoy the "land of the long white cloud" or Aotearoa as it is otherwise known.
I picked up the kiting scene when i moved over here but i can tell you the beaches in Canterbury will be great for what you want they have large empty hard packed sand if you go the right places (and theres plenty we have loads of coast + few people).
And Nelson at the top of the South Isalnd (sorry if it's been mentioned) is where Peter Lynn is from and to my knowledge still flies(if mainly developement flying), plus whenever i went there i always used to look at the guys flying thinking i'd love to do that (looking forward to going home and joining in now i have the gear to).
Although i didn't kite back home i would say i think the second hand market would be pretty average as there just isn't the population, and therefore the amount of people in a minority sport to resell???? This was the case with other sports i did so i imagine it's similar.
Also Kites even when new seem to be more expensive when i looked for my brother over there (Even Peter Lynn!!!!)
i would say keep your kites you'll have loads of wide empty spaces to use them in and you won't want to be stuck without them.
Good luck man, any questions i will be happy to try and answer them. I know Canterbury pretty well (Born in Timaru raised in Dunedin) so although not an actual local i have spent plenty of time there.
Cheers Dave