It turns out the author had another reason to celebrate as her daughter Hayley Stevenson revealed it was her mother's 70th birthday.
"I was trying to keep that a secret," the writer of five books said as the gathered sung Happy Birthday.
Unable to secure an All Black for the occasion, Mrs Stevenson launched the book with the help of grandson Jak (8) who cut the ribbons in a miniature, retro All Blacks strip.
As a member of her target audience Jak - himself an aspiring first five-eight - reckons his grandmother's latest offering is well worth a read.
"I like it because it's about a rugby player and he plays for his own team and he learns lots of lessons in the book." The book is dedicated both to her mentor, Amanda Cushen, of Queenstown, and her Christchurch-based oncologist Dr Chris Wynne.
Mrs Stevenson was diagnosed with kidney cancer that has spread to the liver five months ago, and began writing the book for the upcoming World Cup as she was being treated.
"I was staying at home and, not being well, decided to put pen to paper," she said.
The New Zealand Rugby Football Union-sanctioned book, illustrated by P.G. Rob, showcases Wakatipu attractions and landscapes as well as local school rugby teams and, like her previous work, has a lesson at its heart.
"I like to have morals in all my stories - this story is about a little bully boy people have almost given up on but the coach believes in him."
As a rugby fan she said she "certainly had a lot to learn" about the game.
Saturday's launch was a "way to say thank you to all the people who helped me when I was sick". A donation of 50c from each $19.50 copy of the 3000 print run will go to the Cancer Society and Mrs Stevenson hopes the money will stay in the Wakatipu.
Zac Mac the All Black will also grace at least one US bookshelf before too long - Colorado's Aspen Middle School principal Tom Heald was at the launch to get a copy for the school library.
Queenstown has a sister city relationship Aspen and six high school pupils are in the resort as part of the revived exchange programme with Wakatipu High School - the book will go with the delegation when it heads home on Saturday.
