Clive woman Dennise Ellers will run 3.8, bike 180 and run 42.2 kilometres for her "gorgeous" little neighbour.
She will be compete in IronMan 2016 to raise awareness for the rare heart condition suffered by three-year-old Cameron Bartle.
He was born with hypoplastic right heart syndrome, which basically meant he had half a heart.
At just 12 hours old Cameron suffered heart failure, and at five days old underwent his first surgery.
He had his next surgery at three months old, and is currently at Starship in Auckland after having his fourth open heart surgery.
Ms Ellers said she had the idea of doing the IronMan for Cameron after one of the neighbourhood's regular catchups.
"I just want to see him grow up, and support the family. Anything we can do to support them, we will," she said.
"There's something about Cameron, he just connects with everyone."
Ms Ellers and her partner Graeme had also been running a Givealittle page since April to raise funds for a defibrillator.
Cameron will need one for the rest of his life, and ideally would have one at home, kindergarten and school. With each costing between $3000 and $5000, the couple were hoping just to raise enough for one.
They were also trying to raise money for extra costs, such as the annual, and then biennial trips the family will need to make to Starship for Cameron's checkups.
The rest of Cameron's family, parents Rachael and Nick and older brother Cory, were sticking by his side in Auckland.
They had been there since November 2 for what was meant to be Cameron's final open heart surgery. However he ended up in renal failure. Three days later, the three-year-old had his fourth surgery.
While Cameron recovered he would remain in ICU, but the family had their fingers crossed they would be back in Clive for Christmas.
-If you would like to help out Cameron and the Bartle family, visit givealittle.co.nz/cause/ride4cameron