The couple were married in Dunedin last year, and six weeks ago, just before the birth of their first child, Matteo, Mr Guidi was diagnosed with the most aggressive form of motor neurone disease - amyotrophic lateral sclerosis (Lou Gehrig's disease).
The disorder causes the death of nerve cells (neurons) in the brain and results in muscular atrophy.
Mr Guidi will have difficulty speaking, swallowing and eventually breathing, and has been given two years to live.
A Givealittle page was set up on June 6 to support Mrs Leese Guidi and their son.
The appeal has already raised $24,427.
Mrs Leese Guidi said, in a Facebook message, she was "extremely appreciative'' of the support she had received, and believed it would have a direct impact on making some aspects of their lives "a little easier to bear over the next while''.
"Huge love and thanks to you all, and for the many kind messages we have both received, letting us know you are thinking of us.
"It's unfathomable to me that this terrible illness has struck such a good man at such an important time in his life.
"Your kindness means a lot to us.''
Her father, David Leese, told the Otago Daily Times last night the situation was "devastating'' for the couple.
"It's such a tragedy. For them to come out here, all the way from Italy, and form a new life, a new house, a baby and get a fantastic job, it's just unbelievable this should happen.
"He's such a fine guy. I can't believe that this is happening.''
He said Mr Guidi was the chief winemaker at Heron's Flight in Matakana, north of Auckland.
He had reduced his work hours significantly since the diagnosis.
He said his daughter had also stopped working so they could spend more quality time together.
Eventually, she would become his carer, he said.
Mr Leese said the couple were on their way back to Italy this week, so Mr Guidi could spend time with his family until the end of July.
Mrs Leese Guidi graduated from the University of Otago in 2003, and by 2006 she had graduated from the Benjamin Britten International Opera School at the Royal College of Music, in London, and made her debut at the Royal Opera House Covent Garden.
In 2007, she won the Queen Elizabeth Rosebowl which was presented by HRH Prince Charles.
Until recently, the soprano has had a busy career performing around the world, but has always made time to perform in Dunedin.
The Give-A-Little page said Mr Guidi was investigating treatment programmes for the disease, and the donations would help support his family, while allowing him some freedom to make the most of life - especially while he was still physically able.
A family friend said the news was a terrible shock and "a devastating blow for a new family''.
"Stefano and Anna are both proud and generous people who have given great pleasure to others through their gifts. And now we've a chance to return the favour when they need us most.
"It's a terrible disease that has no cure, so the best thing we can all do is love and support Stefano and his family, to make the most of their time together just now.''
