Helinut,
I have done alot of flying in both the North and South Islands of New Zealand and would suggest the following;
1) The time of year you are intending to go to NZ is smack in the middle of the America's Cup yachting final, hence try and get yourself a machine out of Auckland and do some flying around or near (depending on airspace restrictions at the time) the sailing regatta - it's a spectacular site.
2) As previous replys have mentioned, next stop should be the lower South Island. Try Wanaka or Queenstown for operators most will be happy to do a u-fly scenic trip. If the weather permits try and fly into Milford sound and get a landing (or two) in at the one of the many glaciers on the way back.
3) Forget the one eyed comment of Steve76, he should learn to read.
4) Accomodation can be expensive, but the great thing is that all levels of budget are catered for. Get yourself a 'Jason's' accomodation guide and book your next stop accomodation at least a day or two before.
Best of luck - BigJim
