The money will also go towards buying them school equipment, books, a basic uniform and shoes.
Seventy-four children, many of them Aids orphans, are enrolled in the programme.
Miss Duncan, whom the children call "Mama Mary", is working in Queensland to help support herself. She travels to Africa each year and spends about three months there working on her programme with volunteers.
She described her work as difficult, draining and at times depressing, but satisfying.
"Volunteering in such extreme poverty isn't easy. It is incredibly hard in every way. It is depressing because you feel like no matter what you do, the problem is just too big.
"I have learned more from the kids in my programme than I ever could have at any university hall.
"They have taught me how to appreciate the small things in life. That happiness doesn't come from material objects but instead from the experiences you share, places you go and people you meet."
Her programme is a registered charity and her parents, Andrew and Vinnie Duncan, are directors.
Her mother, who travelled to Tanzania in June, said the programme had turned into a family affair, with their other children now sponsoring some of the children in Arusha.
Mrs Duncan said: "It's absolutely frightful for us as parents when she's over there. We worry about everything, but you also want your children to be independent.
"But seeing what she's done for these children - any parent would be proud."
Miss Duncan said she hoped to develop her programme in the next few years to include more children.
"All of this can destroy you and it takes a thick skin and reminding yourself, which I have to do every single day, that even if after everything I only manage to help one person ... I have changed their life for good. And that's what keeps me going."
Arusha, Tanzania
* Capital of the Arusha region.
* Population: Arusha district: 516,000 people.
Arusha Children's Effort
* New Zealand-registered charity.
* Sponsoring 74 African children.
* Money to go towards an education.
For more information or to donate, visit: arushachildrenseffort.com.