Australia does not have an official au pair program therefore the workaround to go to Australia is to obtain a 1 year working holiday visa.
Visa Information
There are two types of Working Holiday visa: subclass 417 for people from Belgium, Canada, Republic of Cyprus, Denmark, Estonia, Finland, France, Germany, Hong Kong, Republic of Ireland, Italy, Japan, Republic of Korea, Malta, Netherlands, Norway, Sweden, Taiwan and United Kingdom. subclass 462 for people from Chile, Thailand, Turkey and the USA that have tertiary education. US citizens are allowed with highschool education
This visa allows:
If you are granted this visa you can:
-enter Australia within 12 months of grant
-stay up to 12 months
-leave and re-enter Australia any number of times while the visa is valid
-work in Australia for up to 6 months with each employer
-study for up to 4 months.
If you hold a second Working Holiday visa, you may return to work for a further 6 months for an employer with whom you worked on your first Working Holiday visa.