Sport Northland picked up the Ray White Allens Kids Triathlon four years ago - an event held at Onerahi and started by Whangarei sports coach Murray Healey in 2004 - but dropped it this year in favour of the Weet-Bix Kids Tryathlon series.
Sport Northland is contracted to coordinate the Waitangi event, looking after traffic management, marshalls and promotion.
Sport Northland chief executive Brent Eastwood said the big reason for switching to the Waitangi event was the belief it would lead to increased participation. That had been borne out already by record entries.
The Onerahi event was limited by the size of the venue plus holding the triathlon at a central location in Northland made it more accessible to Mid and Far North children.
The Weet-Bix Tryathlon was also a well-known brand with a big marketing machine behind it, the ability to bring in top athletes such as netballer Irene van Dyk, and access to funding.
Although numbers at the Onerahi event were higher in its early days, entries peaked around 650 when Sport Northland was running it, Mr Eastwood said.
Mr Healey, who originally started the Onerahi event when the Weet-Bix Tryathlon wouldn't come to Northland, had mixed feelings about the new event - disappointed that Whangarei was losing its kids' triathlon, but pleased the Weet-Bix event would be held in the North.
"It's a great brand and great for the sport. It'll be great to see all the stars come up to Northland - that's something we often miss out on - and I hope everyone supports it. It's just disappointing that some Whangarei kids will miss out."
Mr Healey believed the event would eventually return to Whangarei where most of the population was. At its peak the Onerahi event had 1000 entries. He was confident it would be a venue again in future.
Individual entry fees in the Weet-Bix Tryathlon range from $35 earlybird to $53 on the day but a $20 subsidy means children from decile 1-4 schools pay $15. A total of 400 discounted entries were available. Fees for the Onerahi event ranged from $18 super-earlybird up to $27 standard.
Sport Northland events team leader Azelia Parkinson said the Tryathlon had been capped at 1200 entries and sold out last Friday.
"That's massive for a first event. The target was 500, so to double that and more is awesome," she said.
The Tryathlon is supported locally by Sport Northland, the Far North District Council, Business Paihia, Waitangi National Trust and Te Tii Marae. Other events sponsored by the Far North District Council include the Bay of Islands Classic swimming race from Russell to Paihia, funded to the tune of $25,000 per year from 2015-17.
Sport Northland has been promoting the tryathlon at low-decile schools, including by making bikes available and helping with transport.