Ms Harris told the children it had taken her a lot of courage to stand in front of an assembly and give a korero, but she wanted to publicly express her gratitude.
"Thank you for upholding what's good in our community. Thanks to these two tamariki I was able to pay my bills and carry on with our weekend, with an extra warm heart," she said.
The mother of three said she was "absolutely humbled" by the children's honesty, saying it had restored her faith in the community.
Mihi said the decision to take the wallet to the police station was simple.
"It was somebody else's, it wasn't ours. I wanted to tell the truth," she said, adding that her Auntie April, the children's great-aunt and guardian, had taught her to tell the truth and be responsible.
A proud April Rihari, who was joined at the assembly by other whanau members, said she tried to do the right thing by the children while also teaching them the right values.
Acting Senior Sergeant Davis said $900 was a substantial amount of money, even for an adult, and the children's decision to do the right thing deserved to be celebrated.