Motuihe has been a Maori settlement, a quarantine station, a prisoner of war camp, a naval training base and a sheep and beef farm. The old woolshed is where the volunteers are split into groups for our day of digging holes for nesting boxes and tree planting.
We're a mixed bunch - families, friends and two high school groups. A teacher asks whether they'll be able to see their campus in the city from where they'll be planting trees.
"No," replies John. "Would you like to work somewhere that you can?"
He wants to ensure the visitors enjoy their day.
"What we've achieved is all down to support from volunteers," he explains later.
"We don't want to send them to a hill where it's blowing a gale or give them a job that's too hard. We want them to come back."
Motuihe is tucked between Motutapu and Waiheke Islands just a 30-minute ferry ride from downtown Auckland.
"We'd love to see more day-trippers," says John.
"There are lovely walking tracks and whichever way the wind is blowing there's always a sheltered beach for a swim and a picnic."
Our group walks to arguably the most picturesque hillside in Auckland to plant native trees. I pause from my work every now and then to gaze across the Hauraki Gulf to Maraetai and Beachlands.
The peace is momentarily interrupted by a squeal from a teenager.
"Oh my God! It's, like, right there!"
Her spade has uncovered a worm. Long-time volunteer Simon Sheen is unperturbed - helping the girls plant their tree before checking on others.
"We meet kids who don't know that trees grow from seeds or who've never been on a boat," he says.
"It's just a completely different experience for them to go places where there's nothing - no road, no shops, no cars."
For those who want to get involved in the restoration, jobs are allocated depending on ability, age or fitness. Even primary age kids can help in the nursery, monitor wildlife, deliver fertiliser or collect seeds in the bush.
After an hour and a half of work, we're rewarded with a barbecued sausage and encouraged to explore. Asher and I gather shells from the stunning white sand beach Calypso Bay and find rope swings tied to gnarled pohutukawa trees. We visit the northernmost tip, Te Tumurae Point, where the naval base used to be.
The highlight of the day, though, is our bushwalk where we stumble across the tuatara.
Sixty were released on the island two years ago, so Asher's find is a vital clue to how well they're doing. John attaches a motion detector camera to a nearby branch to monitor the burrow. Asher is given the honour of switching it on.
We're exhausted and yet still buzzing on the ferry ride home. We chat with some of the regular volunteers - some of whom have historic family ties to Motuihe Island and others, like Simon, who have simply fallen in love with it.
He says being part of one of the Hauraki Gulf's greatest eco-success stories simply feels like the right thing to do.
"It's just good for the soul."
NEED TO KNOW
Anyone can go along to Motuihe Island on the first, third or fifth (if there is one) Sunday of each month (next volunteer day is Sunday April 19).
Choose from a number of different volunteering tasks in the morning, enjoy a free sausage sizzle for lunch, then more volunteering, time on one of the island's beaches or a guided walk.
Volunteers pay $20 for the ferry if they register with the trust.
