The nation's Australian embassy will on Sunday host an event coinciding with the proclamation of Crown Prince Frederik as King.
Diplomats are meanwhile tasked with choosing a gift from Australian taxpayers for the royal couple.
Thousands of people are expected to line the streets of Copenhagen to catch a glimpse of the outgoing monarch, 83-year-old Queen Margrethe, and the new King and Queen as they travel to the Danish parliament for the handover late on Sunday night (AEDT).
The Danish royal palace on Wednesday (local time) confirmed that Mary's eldest sister Jane Stephens, a Hobart-based pharmacist, will travel to the event. She is godmother to Frederik and Mary's eldest son, Christian.
A huge crowd is expected outside the parliament to hear Prime Minister Mette Frederiksen's balcony introduction of Frederik as the new regent. Onlookers will also be hoping to catch a glimpse of their new Queen on the balcony.
Mary's elevation to Queen comes 23 years after she met the Crown Prince at a Sydney pub during the 2000 Olympics. The pair married in 2004 and have four children.
Australian Ambassador to Denmark Kerin Ayyalaraju will host an event for Australians living in Denmark at her official residence on Sunday afternoon to "mark the momentous occasion".
"The fact that Denmark will have a Queen who is from Australia will be such a unique and special connection between our countries," Ms Ayyalaraju told Denmark's TV2 Kosmopol news.
"So many Australians would be inspired by the way that she has embraced her new home."
Queen Margrethe announced her abdication on January 14, exactly 52 years since becoming monarch after her father's death, in a live TV address on New Year's Eve.
Danish media are reporting that Queen Margrethe only told her two sons, Frederik and Joachim, about her abdication plans a few days before the announcement.
Prince Joachim is expected to return from Washington DC, where he works as defence industry attache at the Danish Embassy, but his wife Marie is staying at home.
Queen Margrethe stripped Joachim's four children of prince and princess titles in 2022 to make the Danish monarchy more sustainable.
Interest in the royal succession has hit peak levels in recent days with the palace reporting a media inquiry once every five minutes on average.
Royals from other countries are not expected to attend Sunday's event and the reception guest list is expected to be released on the day.
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