Given name from birth of son search on New Zealand BDM website in November 2018:
1897/7381. Armstrong, Andrew Alexander. Mother: Sarah. Father: Andrew

Maiden name, year and country of marriage from search on New Zealand BDM website in November 2018:
1889/751. Bride: Sarah Duval. Groom: Andrew Armstrong

Full date of marriage of 28 January 1889 from further searching in November 2018 on BDM Search by incrementally changing the date range for the marriage.