There was something magical about Connie Johnson's Big Heart Project on a Canberra netball court on Wednesday.

Five cent pieces glinted in the autumn sun, the sense of camaraderie was palpable, the gratitude to a woman dying from breast cancer and her little brother immense.

People were joyful but also thoughtful as they tossed five cent pieces on to a huge heart of coins on one of the courts.

They will add to the tally of what is likely to be more than $1 million raised for research into all forms of cancer. The expected world record for the biggest heart made out of five cent pieces is due to be confirmed Wednesday evening.

"I've never felt so much love in my life," an elated Connie said.

"Everyone who is here is here for love, for passion, a cure. There's sadness, there's celebration."

The Canberra mother-of-two has terminal, late-stage breast cancer and recently decided to end all treatment.

But, as she retreats from public life and her fundraising and advocacy for the Love Your Sister organisation to concentrate on her own family, she wanted to go out in a big way.

"It kind of feels like a victory lap for Con," her brother Samuel said.

"A chance for her to go, 'You know what?' We kicked cancer in the face and we might as well grab another million before I'm done'. I just think it's so classy."

All money raised from Wednesday's event will go to the Garvan Institute into breast cancer research and other research projects on a range of other cancers.

"I don't care what cancer someone's got, let's get rid of it," Samuel said.

"Whether it's 'rare', whether it's 'popular', whether it's 'trendy'. I hate all cancer and, as far as I'm concerned, they can all go and get stuffed."

Connie's motivation has always to prevent another person having to say goodbye to their family due to the insidious disease.

"When I see on our social [media] more people being diagnosed and reaching out and talking to me, it's literally like putting a red hot poker through my heart," she said.

"The thought of other people having to go through the pain and the struggle, the relentlessness, the financial burden - cancer just seeps through every aspect of your family's life.

"And the thought of other people going through it is just unbearable."

With Samuel and her boys Willoughby and Hamilton, along with "partner in life" Mike Johnson by her side, Connie  threw coins into the air and did a "coin angel" in the heart as she officially launched Connie's Big Heart Project at the Lyneham netball courts. Volunteers used brooms to sweep the thousands of coins into place.

It has been an exhausting few months organising the event but Connie's eyes were shining as brightly as the coins.

"I had a check-up on Monday with a nurse practitioner who's been looking after me for seven years and she said she's never seen me this well. And I think this might explain that," she said.

She and Samuel have already raised more than $4 million for breast cancer research, via Love Your Sister and his unicycle ride around Australia.

Wednesday is an emotional goodbye and thank you to Connie, who has been the public face and quiet force behind Love Your Sister, which has hundreds of thousands of supporters or "villagers" around Australia.

"After tomorrow, I will be retiring," Connie said.

"I will be focusing on my children. And spending the time with them that they need and what I'm desperately longing for.

"We're going to have a nice few months and I just hope my health holds up for a few months, for me and for them."

People lined up from early Wednesday morning to add their five cent pieces to the heart.

Among them was Nicholas Agnew, a year six student from nearby Rosary Primary School at Watson.

He and mum Louise heard about the heart on their drive into school from Murrumbateman. They could only scrap together three five cent pieces from the car console.

"But I thought, 'We're going to take them in anyway'," Louise said, with a laugh.

They were given a bucket of coins by volunteers to throw on the heart. For 11-year-old Nicholas, the gesture was personal.

"A really close family friend had breast cancer," he said.

Seven-year-old Eve Doble travelled from Oyster Bay Public School in Sydney with her dad Matt to add the $973.35 in five cent coins the school raised for the cause.

Mr Doble, an electrician, got the school involved in the fundraiser.

"Oh, it just got me," he said.

"So we spoke to the school and off we went. It also teaches the kids to help others."

Helen Barker of Gowrie came with her grandson, Brooklyn Shevlin, 20 months, bringing her plastic bag of five cent pieces with her.

"I don't think there's any family that has not been touched by cancer," she said.

Belinda Barnier is the Leukaemia Foundation ACT business development manager but "will raise money for anyone" as she brought in her bag of coins, collected just during her morning walk around Yarralumla and Braddon on Wednesday morning.

The Royal Australian Mint has lent 4 million five cent pieces for people to add to the heart. Mint CEO Ross MacDiarmid said they were brought in by truck in drums weighing 750 kilos each.

The coins will return to the Mint but the dollar value of the contribution from the public will be added to the tally.

"It's our contribution to breaking the record," Mr MacDiarmid said.

"It's an absolutely amazing project, just the logistics of it for a start.

"Someone a moment ago said they drove down from Sydney with three suitcases full of five cent pieces. That's some indication of the way they have captured people's attention around the nation."

Looking frail but elated, Connie was happy to receive hugs and take photographs with her supporters.

"It's lovely, it's so beautiful," she said.

"It's just the best in everyone here. And it's an honour and a privilege to meet each and every one of them."

Samuel was full of beans, promising to hold off a nudie run because it's a family event, but allowing anyone who wanted to hold his Gold Logie.

"I think that we're going to reflect on this day for quite a few months to come and it might take that long to process it all," Connie said.

Both Samuel and Connie praised Canberrans' generosity. While the Big Heart Project has been a national endeavour, Canberra has been the focus of it and Love Your Sister as Connie made the national capital her home.

"She might have been born in Victoria, but she will absolutely leave this world a Canberran," Samuel said.

Connie said Canberra was simply home.

"I love this town," she said. "And it's got a big heart. Literally."

* The Big Heart Project is at the Lyneham netball courts at 435 Northbourne Avenue until 8pm on Wednesday. There are lots of activities for the kids, food and drink vans and information stalls. People can continue to donate their five cent pieces right up until 8pm.