Romans Cottage, Adams Cottage and Granny's Cottage are all registered by the New Zealand Historic Places Trust as category 2 protected buildings and date back to the 1800s.
In February 2007, former owner and Irish developer Eamon Cleary was accused of destroying the cottages by "wilful neglect" before the Queenstown Lakes District Council struck a $1.9 million deal with Lake Hayes property developer John Martin.
Mr Martin bought the cottages from Mr Cleary and then sold them to the council.
The Arrowtown Trust was then established to oversee the restoration of the cottages at 59, 61 and 65 Buckingham St.
Trust member David Clarke said the restoration job was finally complete and the trust thought it fitting the town - which held an impromptu street party the day the news broke of the deal Mr Martin struck with Mr Cleary and the council - celebrated the achievement in style.
"We're just marking the point where the cottages are finished, the church [the former Miller's Flat Church relocated last year] is finished and we wanted to formally say to the council 'here it is' and have a little party.
"There has just been a huge number of people ... that have supported it [the restoration]: all the funding agencies that have given us money, Bagley Builders and their subcontractors, local architects that got together to workshop the concept, landscape architects and the likes of the Horticultural Society and Jean Britton.
"While we couldn't afford to buy booze for the whole town, Provisions [cafe] is baking a cake and we'll have some punch to toast the cottages."
In all, it had cost "close to $3 million" to restore the three cottages and the Miller's Flat Church with funding from the council, the Central Lakes Trust, the Community Trust of Southland, the Trusts Charitable Foundation and the Lotteries Grants Board.
The council now had a "valuable collection of buildings" which were providing a return from tenants, Mr Clarke said.
One of the cottage's tenants is Provisions cafe, and owner Jane Shaw said the cottage had provided the "perfect home" since it opened in July last year.
"The trust was fantastic to work with; they were very, very encouraging and supportive and really helped us bring Provisions to Arrowtown.
"A lot of people [who visit the cafe] have personal links to the building. Quite an extraordinary number of people say 'I used to live here,' 'My aunt used to live here,' 'My bedroom was where the kitchen was.'
"It's quite amazing. It's lovely knowing it's a public space now," Ms Shaw said.
The cafe would be responsible for baking a large cake to mark the occasion on Sunday, and the recipe would possibly be the same as for the recent Royal Wedding cake, she said.
Mr Clarke said festivities would begin in the gardens behind the cottages at 2.30pm, the Journeymen Jazz Group playing before some short official speeches at 3.15pm, followed by the Miners Band and the Buckingham Belles performing before the 2011 RWC final.
