This article from Clutha Leader 9 January 1920 (click on link) may help to answer some of your research questions. Providing it is the correct family.
A check on BDMNZ has the following births 1860-1880 with parents named as Margaret & John:
1860 - John; 1861 - John; 1863 - Jessie; 1867 - James Alexander; 1869 - Mary Ann; 1873 - John; 1873 - Isabella Jane; 1876 - Margaret.
There is a reasonable amount of info available on the above family from Warepa and Roslyn.
Cheers from Scotland - Séan