Changing Visa from Partner of a worker Visitor Visa to AEWV

Hello, I would like to ask regarding the changes that will happen to our visa, I came in New Zealand under partnership Visit Visa with my dependent children, since my AEWV is on process I also plan to change the visa of my two children to student visa, however I have a baby (18months) also with dependent visit visa, do I have to apply for my baby a new visit visa or his old visa will retain? Thank you.