Mr Sutherland was diagnosed with advanced melanoma just last month, after his wife noticed a raised mole on his back.
"After 18 months of working tirelessly to get Lachie through his intensive treatment, to now be confronted with this new reality is unimaginable," Mrs Sutherland said at the time.
Her husband showed "the same tenacity and determination" as his son, who had offered incredible insight to support his father's battle, she said.
"It's a bizarre scenario to watch a 5-year-old comforting his father, and realising he's better equipped and qualified for the role than most of us."
The Sutherlands had been overwhelmed with support through TouchPauseEngage - named to reflect Lachie's love of rugby and created through the zero-fees fundraising service, givealittle.co.nz.
Family photographs and moving messages detailing their plight were frequently posted to keep family, friends and supporters up to date.
Donations had helped the family to travel to Australia for Lachie's treatment.