Hello Janet,
A couple of things.
1. That batch of Glasgow Associate Session records is one of those infuriating batches where the LDS have extracted only
females into the online IGI. If one ordered the relevant film in to one's local LDS Family History centre, it would probably list the boys as well.
The pre-1855 baptisms won't be found on ScotlandsPeople which includes only OPR entries i.e. from the established Church of Scotland.
2. The Queensland, Australia historical indexes (1829-1914 for births; to 1929 for marriages and deaths) of BMDs can be searched online free at:
http://www.justice.qld.gov.au/829.htmThe trigger for searching these was Monica's great find on SP of a 1900 Will for a Robert MACGAVIN in Queensland.
Fortunately, there are relevant records which indicate that the family was in Queenland before the UK 1871 census.
They include:
Marriages1866, Mary Reid MCGAVIN to Henry MARSH
Deaths1868, Jessie Skelly MCGAVIN, parents Robert MCGAVIN & Margaret SKELLY
And here is mother Margaret's
death:
1886, Margaret MCGAVIN, parents John SKELLY & Janet BOYD
And those of sons:
1921, John Adams Skelly MCGAVIN, parents Robert MCGAVIN & Margaret SKELLY
1925, James MCGAVIN, parents Robert MCGAVIN & Margaret SKELLY
Anyway, you can have a search yourself for other relevant records

And then you might wish to post on the Emigrants to Australia board (with a cross-reference to this thread).
JAP