Ms Manukau told the Herald she could not understand why they would bring the child with them.
"To me it seemed like a family thing, I couldn't believe it."
She thought the child was aged about 2 and the adults looked to be in their 20s.
"We must have disturbed them because they had been in the house and apparently took a computer. When I [saw them] they must have been going back."
When the woman realised she had been seen, she sped off the property, leaving her co-offender to escape on foot, probably over a back fence.
Ms Manukau said the child looked frightened, gripping the seat tightly and looking around.
"What were they thinking with a child? It would be different if it was just guys but still not right."
Htoolar Wah Shwe, 18, was devastated by the loss of her computer, which she needs before school begins at the end of the month. But worse than that was the sense of violation and invasion of space the family had.
They arrived in New Zealand as refugees and came here to feel safe, but the weekend burglary has left them uneasy.
"It wasn't nice. My mum was so worried, so sad. We've been here six years and that's the first time this has happened in our place."
Counties Manukau police spokeswoman Ana-Mari Gates-Bowey said police were investigating.
Last May, a man tried to rob two Ngaruawahia dairies at gunpoint while an 11-month-old and its teenage parents waited in a car outside.
When armed police stopped and confronted them, the mother got out of the car cradling her baby.