"It suits me," he said, bouncing Croibhusha on his knee.
"They hire you to be available to do work as it comes in."
With his wife's job, it was better for him to be able to be at home for the children, rather than working on a contract that would have him heading off overseas.
"When I was in offices I managed projects. I would be responsible for looking after recruitment of personnel, resources, writing project documents.
"In the field, like in Vietnam, I was directly hands-on."
Mr Frewen had numerous stories from his work in developing countries, where he would find internally displaced persons (IDPs) living in sugar factories or old hospitals.
IDPs are people who have to flee their homes, but still remain within their country's borders.
Mr Frewen said they would see families crowded together in buildings with tarpaulins hanging down between them while water dripped down inside.
Just last year Mr Frewen went to both Pakistan and Africa, writing project documents and doing work in the field, where he would find children whose parents had disappeared or been killed.
"At one distribution centre, this woman was crying. Her four sons and husband had been taken away and killed.
"People think about refugees, they don't understand why people leave. It's not like 'oh, we want to go for fun'. You're leaving your family, you're leaving your home."
Part of his work was income generation and creating jobs for people. He worked for the UN's Office for Project Services (UNOPS).
Mr Frewen joined the UN because he hated inequality.
"I just think it's shocking, basically. It's just wrong to see."
Mr Frewen made the decision to move to New Zealand after some time in Australia.
He said the quality of life for his children was important, and there were many more extra-curricular activities available for kids here compared to back in Ireland.
His 5-year-old was doing gymnastics, speed rollerskating, and learning the drums.
"I want them to really enjoy their youth."
He also thought people in Wanganui were particularly friendly. "You walk around and people say hello," he said.
With four master's degrees and one bachelor's, he had never once been to a graduation.
"I've never done these things for the paper," he said. "For me, having a qualification does not make you more intelligent than the next person. I really can't stand intellectual snobbery."
Mr Frewen holds master's degrees in film and television, which he studied in Ireland, social anthropology from Vietnam, international relations from London, and public international law from Melbourne.
"Let me tell you, the master's are far easier than looking after the kids."