He is their third child and first boy, giving sisters Leilani, 3, and Savannah, 1, a little brother. They had kept the sex of the baby a secret so it was a surprise, but they already had the name picked out.
Mr McAdams said the birth went pretty smoothly, thanks to their midwife.
Leilani and Savannah were excited to meet their brother.
"Savannah didn't want to share the baby with anybody," said Mrs McAdams.
The family moved to Masterton from the Solomon Islands three months ago but Mrs McAdams has lived in New Zealand before as her parents live here.
The McAdams said they decided to come back as Savannah was reaching school age and there was better schooling and health care here.
"In the Solomons you give birth on an iron bed with wooden slats to put your legs on," said Mr McAdams.
Their midwife Karen Forest said the maternity ward had been quiet with John the only baby born so far for 2015.