Hi Sue,
Yes you have the right Dorset. There is no passenger list surviving for the Dorset in Adelaide only a newspaper report. The Convictions website has a also a copy of the ships passenger list which gives her name as Mr. Mary Ann McCorkill. The children do not belong with her as seen on the other passenger list, I believe she was probably working as a nanny. She married 11th January, 1853 so the other passengers dont fit. The 1851 census of Penninghame has him as Robert Corkal born Isle of Man only. The death index gives his parents as Peter Corkell and Elinor Claque. I have not downloaded the full certificate yet but will do so. I don't know how to get a copy of the Convictions passenger list which is probably in Sydney and I can't find her on a ship into Sydney. I also have not found her as a convict.
Robin