Hi. What course are you studying in NZ? For some courses, so long as you and your wife can prove partnership for at least a few months, preferably a year, you wife can join you. You can apply at the same time for the dependent child of a Partnership-based Work Visa holder to get a visitor visa. It all depends on whether you are on a course that is listed on the LTSSL or a post-Grad qualification. Later residence possibilities should be straight forward so long as you have the evidence and also either a court order or the child's father's permission to take him from his own country.