Organiser Daniel Cummins started the HeartKids fundraiser in honour of his brother Will, who died at the age of 12 from a heart defect he'd had since birth.

Mum of 10-year-old HeartKid Thomas, Sarah Henderson-Smith, said the event provided not only a great way to raise money and awareness, but it was a way Thomas could get involved in sport without too much physical exertion. In between races on Sunday, HeartKids get to ride in the cars that only go a bit slower with their precious cargo.

"He's going pretty flipping fast," Thomas said, during a practice lap at the hillclimb track.

Thomas was born with a heart defect that means he has a lower life expectancy, and limitations on things he can and can't do.

Sarah said since Thomas saw his first hillclimb six years ago, he has been waiting for the day when he can get in the driver's seat.

"It's not the prolonged physical exertion, it's all right for him to do it."

Sarah said because it was something that makes him excited and happy, they were willing to let him have a go.

"We've been really fortunate with Thomas," Sarah said, referring to the fact that his body has adapted well to his heart defect.

"Life expectancy is decreased, but in saying that, every year there is more research going into childhood heart disease."

There is an operation available, but the success rate is very low, Sarah said. She hopes that with more funding put into research, an operation will become available that could cure Thomas' heart.

"We're lucky [that Thomas is otherwise healthy], which is why we do what we can for HeartKids, and to raise awareness and raise money for research. We're fortunate, but a lot of kids don't go as well as Thomas does."

The HeartKids hillclimb fundraiser event is free for spectators. The event is at the hillclimb track on Sutton Road, near the driver training centre, from 9am to 4pm on Sunday.