The couple are well liked in the area and have been seen holding hands across the table while out for dinner.
The Topp Twins' agent, Arani Cuthbert, said the rights to the ceremony had been sold to a women's magazine and she'd "been sworn to secrecy" so couldn't give details.
In an article in Woman's Day last year that announced their engagement, the couple revealed their marriage ceremony will be a "big, old-fashioned country-style hoedown", with Ms Luxton wearing a "Dolly Parton-style" dress.
They told the magazine how they coped with Ms Luxton's growing realisation that she loved Topp.
Topp proposed the pre-school teacher during a Bali holiday trip last year. They met at the Methven A&P show in 2005 at which Ms Luxton was supporting one of her sons, a singer then aged 11.
Cameron Luxton went on to become a support act for the Topp Twins at events such as Australia's Tamworth Country Music Festival.
On Wednesday, a parliamentary select committee recommended that a bill to legalise same-sex marriage be passed into law.
The legislation's second reading will be held on March 13.
It passed its first reading by 80 votes to 40.