The couple got engaged last Easter at Mahia during a break at Gayford's family bach.
He proposed to her at the top of a hill with a diplomatic protection squad officer nearby.
They have a 19-month-old daughter, Neve, who recently accompanied them to the Labour caucus retreat in Martinborough, to Ratana and will be at Waitangi this week.
Ardern has been to a couple of weddings this year in Wellington, including one at Premier House.
She gave her approval for the wedding of Education Minister and old friend Chris Hipkins to Jade Paul to be held there.
She also attended the wedding of one of her press secretaries, Kelly Spring, to one of Grant Robertson's press secretaries, Alex Tarrant, at Day's Bay.