Several Federal Members of Parliament have stated in the past week that there are no children in detention. If your MP makes the same statement, suggest to them that they go to their own Government's publication:
To check this yourself, copy the link and paste onto your browser (google)
Immigration Detention & Community Statistics Summary 30th September 2017 page 43, the document states that there are 43 children in the RPC on Nauru (Regional Processing Centre).
Information from Ian Rintoul of the Refugee Action Coalistion Sydney is that there are 106 refugee children released from the RPC into the Nauruan community. This does not include 29 young people who turned 18 after arrival in Nauru, and now living in the Nauruan community.