Apart from the marriage of Michael Omeara and Mary Smith, I could only find the birth of one child to them on 29 Sep 1859 in Adelaide Book 15 Page 189.
There is a Johanna Omeara who arrived in 1877 on the 'Rodney' according to a book I have but she may not be connected at all -it's a long shot. Her father is Daniel and she is from O'Briensridge Ireland.She married a Joseph Silver.If she is connected I suggest you check out the set of two booksSouth Australians 1836 -1885, Published by South Australian Genealogy and Heraldry Society (SAGHS)1990. There is an entry in there for her and husband. You should be able to find the book in a Public Library that has a good genealogy reference section.There are other sets of books of the same name published different years, they have different information in them but worth a look.
The SAGHS on Unley Rd, Unley may be able to help you if some one is researching the same family.(08) 8272 4222 or Fax (08) 8272 4910.(I am not a member)