Do I need a special drivers license to ride a bike fitted with sidechair. This is not the case in Denmark wherefore I do not hold such permission. Further more, do we need an “International Drivers License?

No, in NZ all you need is an unrestricted motorcycle licence. Your Danish one is sufficient, you don’t need an International Driver’s Licence. From my perspective, I only need to be re-assured that you have had reasonable experience piloting a chair….