Registering Children for Pre-school in Australia

Hi, I am a kiwi with a family (wife + 2 and 4 year old) who had been living overseas. I have found a job in Sydney, and am currently working here, while my wife's visa and children's NZ passports come through.

Now the kids NZ passports have come through and they are going to come over and live with me in Sydney. I have got medicare, centrelink etc set up on 'MyGov' but how do I go about listing my kids as dependents, and how do I apply for preschool benefits?

Preschool costs $100 a day, and having two kids on it would sink us financially.

It is really hard to get information about this, so really looking forward to anybody sharing their experience on this matter.