"There are a lot of fit kids up here that are keen on participating but their parents can't aford [sic] to take them on a five hour drive," wrote Josh, adding he was "annoyed" there wasn't a closer event.
"We can not go to any events because parents have to work at packing things up and they have to pay for travelling," wrote Leon in his letter.
Organisers of the long-running event received the letters, and set about planning to host a TRYathlon further north.
"The whole idea behind the Weet-Bix Kids TRYathlon is for as many Kiwi kids to take part as possible to get the health benefits and confidence boost it gives them, so we took notice when we received the letters from Pukenui School," Sanitarium's executive general manager Pierre van Heerden said.
"The enthusiasm of Northland children to attend the event has been so high in the past, we have even heard of parents and children driving down the day before and sleeping the night in the car. Now, for the first time, we have an event in the Bay of Islands, which makes it far more accessible for Northland children, and hopefully means even more can experience the fun of a TRYathlon."
The two passionate letter writers, now in Year 8, are pleased to have been able to help make it happen.
"I feel sort of proud and happy," says Josh, while Leon adds that he's feeling "pumped up" about the effect their letters had. The two boys will be travelling to the Waitangi event together and participating as a team in the TRYathlon, where they are looking forward to "having fun and doing the best we can", says Josh.