The band will play at the Castle Hill RSL in New South Wales on January 17 and 18.
"We didn't know how big (it would be) or if anyone would turn up," Field said, according to 7 News.
But the band is hoping they can do a national fundraising tour at some point.
"We'd love to go to all the cities and raise money," Field said.
Celebrities in Australia and around the globe have joined fundraising efforts, with more than $30 million pledged to the NSW RFS through comedian Celeste Barber's Facebook fundraiser.
American pop superstar Pink has donated half-a-million dollars and encouraged her 32 million Twitter followers to dig deep.
While Chris Hemsworth and his family are the latest in a long list of celebrities that have donated money to Australian bushfire relief efforts.