Family violence was also a contributing factor in the deaths of six babies who died within their first 28 days in 2009.
Ms Sweeney has established a Facebook group called Stop Death by Abuse of our Children which has gathered more than 11,500 followers since her house was tagged after she was seen speaking to police after baby Serenity's death.
Police have not made any arrests over Serenity's death but are still investigating.
Ms Sweeney has picked up the label the taggers gave her - "nark" - and turned it into a lobby group, Nation of Advocates for the Rights of Kids.
"I wanted the community to get together so they could talk about the abuse levels and what we as a community could do about it," she said. "It's not the politicians, it's not only the whanau. It's the community."
She wants people to place soft toys at more than 200 war memorials around the country on the morning of Saturday, September 3, and is recruiting co-ordinators to deliver the toys afterwards to women's refuges and the Salvation Army.
Wellwishers have already started sending her soft toys, including a mascot for the Brisbane Broncos league team sent by the partner of Kiwi-born Bronco Jordan Kahu.
Women's Refuge chief executive Heather Henare hailed Ms Sweeney as "a real champion for change".
"She is a person who wants to see something change in this country about the safety of children. What a wonderful way to do it."
Returned and Services Association president Don McIver said veterans would support the initiative.
"Our veterans fought and gave their lives for the preservation of our democratic way of life and for the preservation of the individual safety and freedom which we all cherish. The community war memorials around the country act as a stark reminder of the sacrifice they made," he said. "While the use of the memorials as a focal point for the NARK campaign on September 3 might not fit strictly within their original purpose, I am sure that the veterans themselves would have seen this cause as a most worthy one, providing the dignity of the memorials is preserved."
ROLL OF SHAME
Deaths from intentional injury, children aged 28 days to 15 years:
* 2004: 13
* 2005: 5
* 2006: 7
* 2007: 5
* 2008: 5
* 2009: 9
Source: Child & Youth Mortality Review Committee