I spent quite a bit of time extracting bits of information from my files and searching online records and the 1851 census extract shows I seem to have found all 8 of the McIntyre children. Brief outline-
Thomas McIntyre (d.bef.1861?) m. Catherine Doherty (c1813-1885 Coleraine)
1.
William McIntyre m.(1856) Elizabeth Wallace- family
2.
John McIntyre (c1834 Ire.-1863 Scot.)
3.
Thomas McIntyre (c1835-1890 Bovagh) m.(1861) Mary Jane Chestnutt- family
4.
Wilson McIntyre (c1841 Ire.-1900 Scot.) m.(1862) Jane Gage
5.
Annie/Nancy McIntyre (c1851-aft.1911)
6. Mary Jane McIntyre (c1852-1921 Scot.) m.(1873) John Cassidy
7.
Catherine McIntyre (c1857-aft.1901) m.(1871) John OBrien- family
8.
Elizabeth Eliza McIntyre m.(1888) William Letson. Family
2.
John McIntyre (c1834 Ire.-1863)
1861 Census:
https://www.freecen.org.uk/search_records/59c54961f4040bbce0d16efd/john-mcintyre-1861-renfrewshire-greenock-1836-?locale=en (John McIntyre, 25, born Ire.)
Death:
https://www.familysearch.org/ark:/61903/1:1:XS6P-NL9V?lang=en 4.
Wilson McIntyre (c1841 Ire.-1900 Scot.) m.(1862 Greenock) Jane Jeanie Gage (d.1905)
Birth:
https://www.familysearch.org/ark:/61903/1:1:6TLL-4441?lang=en 1861 Census:
https://www.freecen.org.uk/search_records/59ef9a2bf4040b559686fea3/wilson-mcintyre-1861-renfrewshire-greenock-1840-?locale=en (lodger Wilson McIntyre, 21, born Ire.)
Greenock Telegraph, 20 Sept.1900: Wilson McIntyre, husband of Jane, died at 14 Blackhall Street, Greenock on 18th September 1900 age 58.
Greenock Telegraph, 20 Feb.1905: Jeanie Gage, widow of Wilson McIntyre, died at 9 Bearhope Street, Greenock on 19th February 1905.
I haven't looked for further records of Wilson in Scotland.
5.
Annie/Nancy McIntyre (c1851-aft.1911)
1901- Annie with sister Catherine; 1911- Nancy with OBrien family
More to follow when I get back home.
Regarding Mary Jane's birthplace- she was almost certainly born in Co. Londonderry, Ireland not Co, Donegal.
The baptism in Dec.1879 is interesting. Mary Jane McIntyre (Church of Ireland) married John Cassidy in Scotland in 1874 and son born Aug.1879 in Ireland. A few months later there is the adult baptism- wonder if son was baptised in Ireland or Scotland as a Catholic around that time.
Added- no baptism for John Cassidy in Errigal or Coleraine R.C. parishes in 1879. Unfortunately St. Guaire's (COI), Aghadowey baptisms don't start until 1882. St. Paul's (COI), Garvagh baptisms start 1873 but are in local custody.