Do you need to apply for a NZ passport for your child?
If your child was born outside of NZ you will need to apply for citizenship by descent before being able to apply for a NZ passport. Note: Your child may not be able to pass on their NZ citizenship status to their children due to never living in NZ or not applying for full citizenship.
"The registration of your citizenship confirms and provides evidence of your status as a New Zealand citizen by descent. It does not enable you to pass on New Zealand citizenship to any children that you may have who are born outside New Zealand. You may wish to contact the Citizenship Office to determine your eligibility to apply for a grant of New Zealand citizenship. Any children that you have who are born outside New Zealand after you have received the grant of citizenship may have a claim to New Zealand citizenship by descent." http://www.dia.govt.nz/Pubforms.nsf/URL/ApplicationforRegistrationofNZCitizenshipbyDescent.pdf/$file/ApplicationforRegistrationofNZCitizenshipbyDescent.pdf
Cost from Sydney is $180 as of 06/06/2014. To view prices: http://www.dia.govt.nz/diawebsite.nsf/wpg_URL/Services-Citizenship-Citizenship-Application-Fees-and-Forms?OpenDocument#five
Required Documents: http://www.dia.govt.nz/diawebsite.nsf/wpg_URL/Services-Citizenship-Citizenship-Application-Fees-and-Forms?OpenDocument#five