VIC Mortgaged Property as Security allowing children travel

Hello,

I seek to take my children 16 and 12 and a half years old overseas.

Their mother is requesting that my property be provided to the court as security.

I have the Register Search Statement (Title) document

I am representing myself and have filed all papers via www.comcourts.gov.au Commonwealth Courts Portal.

Final Orders Application before Senior Registrar is on 30 July

The Questions
How and when do I fulfill the mother's request?

1. Is there a special Application that I need to submit - Before the day - to have the property effectively Security For the Court
   OR
2. Do I seek court orders to that effect on the day for the court to have the property as security?
   OR
3. Offer a Power of Attorney to the Mother's Lawyer representing the mother to allow them to act if I don't return the children due to malevolence
   OR

How do I offer the Mother's Lawyer these options both on the record and off the record - so how do I send correspondence that is admissible on the day and correspondence that is not - to negotiate fulfillment of their request.

Thanks in advance
Regards