Since they have their Canadian passports they do not need a US visa or ESTA for this trip regardless of their dual Aussie nationality.

In most circumstances, Canadian citizens do not require visitor, business, transit or other visas to enter the United States, either from Canada or from other countries.

Source: U.S. Embassy & Consulates in Canada

There are some exceptions but your trip does not fall under those, you can read about the exceptions on the link above.

Since they have their Canadian passports (and will travel to the US with those) they do not need a US visa or ESTA for this trip regardless of their dual Aussie nationality.

In most circumstances, Canadian citizens do not require visitor, business, transit or other visas to enter the United States, either from Canada or from other countries.

Source: U.S. Embassy & Consulates in Canada

There are some exceptions but your trip does not fall under those, you can read about the exceptions on the link above.

Since they have their Canadian passports they do not need a US visa or ESTA for this trip regardless of their dual Aussie nationality.

Since they have their Canadian passports they do not need a US visa or ESTA for this trip regardless of their dual Aussie nationality.

In most circumstances, Canadian citizens do not require visitor, business, transit or other visas to enter the United States, either from Canada or from other countries.

Source: U.S. Embassy & Consulates in Canada

There are some exceptions but your trip does not fall under those, you can read about the exceptions on the link above.