Hello Dianne,
The ship which brought my ggg uncle Andrew Hepburn (1801 - 1873) and 1st cousin 4 times removed George Sinclair (1800 - 1875) to Otago in 1857 was the "George Canning." Several other members of the related Hepburn and Sinclair families and spouses were also on this ship including my great grandfather William Hepburn (1834 - 1887) and my 3x great grandfather James Paterson (c1776 - 1861).
It was George's daughter Mary (1836 - 1936) who married John Wallace in Dunedin in 1861, not Mary Murray Sinclair (c.1873 - 1913) who was a single woman. James Spencer Hepburn Wallace (1877 - 1916) was the 7th of 9 children of Mary & John.
I have more information about the Sinclairs and Hepburns researched in the years since I last contributed to Rootschat. It would be easier by normal email if you're interested in more details.
Don Hutton