Name, year of birth and death, from Australia and New Zealand Find a Grave Index for son, found in April 2019:
Name: William John Ferguson
Father: William Ferguson 1851–1929
Mother: Elizabeth Ferguson (Buchanan) 1851–1914
URL: https://www.findagrave.com/memorial/143732168

Full date and place of birth and death from:
https://www.findagrave.com/memorial/116962353/william-ferguson

Year and country of marriage from search on New Zealand BDM website in April 2019:
1874/10714. Bride: Elizabeth Buchanan. Groom: William Ferguson

Full date of marriage of 12 August 1874 from further searching in April 2019 on BDM Search by incrementally changing the date range for the marriage.