Know The Loopholes
In most circumstances, before a person can start court proceedings about children, that person and the other parent have to try to resolve the dispute over the children with a counsellor called a Family Dispute Resolution Practitioner. Only if the counselling fails, and the counsellor provides a certificate that it has failed, can the person then start the case.
What you and your co-parent say to the counsellor is private and evidence cannot be given about it in court. The idea is to encourage both parents to speak freely. However, there is an exception. Most counsellors hold what they call intake sessions. These are usually individual but sometimes joint, and are meant to be just introductory to the process. Those intake sessions are not private, and evidence can be given about what happens at them.
You should be aware of this loophole. The Family Law Section of the Law Council has raised the issue to try to get the loophole closed but at the moment it is still open.