Não , nenhum de vocês precisa de um visto de trânsito para a Austrália, contanto que seja abaixo de 72h.
Citando o australiano sobre o assunto (ênfase minha):
The following categories of travellers are eligible to transit through Australia without applying for a visa:
Citizens of the following countries:Andorra, Argentina, Austria, Belgium, Brunei, Bulgaria, Canada, Chile, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Federated States of Micronesia, Fiji, Finland, France, Germany, Greece, Hungary, Iceland, Indonesia, Ireland, Italy, Japan, Kiribati, Latvia, Liechtenstein, Lithuania, Luxembourg, Malaysia, Malta, Marshall Islands, Mexico, Monaco, Nauru, Netherlands, New Zealand, Norway, Oman, Palau, Papua New Guinea, Philippines, Poland, Portugal, Qatar, Romania, Samoa, San Marino, Singapore, Slovakia, Slovenia, Solomon Islands, South Africa, South Korea, Spain, Sweden, Switzerland, Thailand, Tonga, Tuvalu, United Arab Emirates, United Kingdom (including its colonies), United States of America, Uruguay, Vanuatu and Vatican.
No entanto, como Calchas observou, você precisaria de um visto adequado se precisar verificar novamente suas malas
If passengers are required to pass through Immigration clearance and check-in to their onward flight, including managing their luggage, they will require a visa to enter Australia. An appropriate visa for this purpose will need to be applied for and granted before travelling to Australia.