You can include your dependent children in your visa application when you lodge your application.
If you lodge your application and later decide to add a dependent child, you can ask the department to add them to the application. You must do this, in writing, before a decision is made on your application. Complete and send Form 1022: Notification of changes in circumstances to the office that is processing your application.
“If you lodge your application and later decide to add a dependent child, you can ask the department to add them to the application. You must do this, in writing, before a decision is made on your application. Complete and send Form 1022: Notification of changes in circumstances to the office that is processing your application."