It's the culmination of two months of rehearsals on the third peak, Te Mata, with father Paul as well as the Eskdale Park track in Napier.
The pair, calling themselves Dad/Son Specials, are competing as a team with the older Gouldsbrough doing the shorter but more daunting Mt Erin (14km) and Te Mata (12km) legs.
"I'm nervous but really excited. If I do it in about two hours I'll be quite happy," says the youngster who has trained after school and at weekends.
"When I'm older I'll do them [the three peaks] all by myself - maybe when I'm 13 or 14."
Paul, 43, an electrician who arrived in New Zealand 13 years ago, is competing in his sixth challenge.
"Ben's thought about doing it so we bought him a better bike."
He had impressed on his son the need to prepare well because it won't be a given today.
Long rides, taking in 31km up and down Te Mata, were on the agenda for Ben to conquer the longest climb at Mt Kahuranaki.
"I told him that if he doesn't keep up with the training it'll be a pretty miserable experience but he's never complained. He has good work ethics."
Because Mt Erin and Mt Kahuranaki are primarily private property and inaccessible for training, Ben has had to rely on his father's experience and knowledge for his preparation.
"Once he's done the longest climb there's lots of smaller hills and a river crossing to the Mt Erin transfer," Paul explains.
Pivotal to the choice of Ben's peak is that he doesn't have to carry his bike through the rugged terrain.
"Ben hasn't got the height to lug the bike so for safety reasons Mt Kahunaraki is the most suitable," he says, emphasising his son still has to put his bike over four fences at an up-and-down segment known as the Rollercoaster.
"I'm really proud of him because he's shown quite a bit of mettle."
Paul started cycling on roads in Hertfordshire in his early 20s.
"The terrain in England was nothing like here. It was mostly flat and nothing exciting to fire you up."
He and Ben also compete in the Ramblers Cycling Club cyclocross winter series with the latter competing in the under-15 category.
"Ben's never finished last. He was always in the middle of the pack."
Event organiser David Tait says at least 500 people are expected to compete in the walk/run and biking sections today. The mountainbiking section has 47 individual riders as well five two to three-person relay teams.
"[The numbers] are slightly down on last year because of the Cricket World Cup and Relay For Life," Tait says.
