Behave. NZ is the last refuge of Ten Pound Pom gingers whose last act in the UK was to sell their Radio Rentals telly and leave no forwarding address. It's also where they send the ugly Aussies. No offence.
I'd say what a combination of the other posters have said so far
- spend some time in Singapore on the way out (3 days is probably enough) and Thailand on the way back (a week minimum)
- don't try and see it all (it takes 6 or 7 hours just to fly over it!). for a first visit the East coast is...