It should have name of father, and witnesses might be relative of George.
The marriage certificate for mother Mary to Mr Clark would be useful, assuming in SA or NSW.
What names does George give his children please...anything less common...family names used as given name etc?.
I wonder if they arrived with some other name.
What occupation does George have?
Thinking aloud now, because something is not right here, should be more people in this immigrant family to South Australia.....
If Mary Ann arrived in SA, aged 40+, with one very young child, she must have paid for fares...some money, independent means.
Would she be an assisted migrant...sole support for dependent child....who would become responsibility of state if she dies?. Sounds unlikely that Mary and a very young George would be accepted as assisted immigrants?.