"Scotland Births and Baptisms, 1564-1950," database, FamilySearch(https://familysearch.org/ark:/61903/1:1:XBSH-2RN : accessed 29 March 2016), Christy Mackay, 07 Nov 1803; citing PORTREE,INVERNESS,SCOTLAND, reference ; FHL microfilm 990,671.
Born 1803 but father was Donald - possibility, maybe.
"Scotland Births and Baptisms, 1564-1950," database, FamilySearch(https://familysearch.org/ark:/61903/1:1:X18L-3ZR : accessed 29 March 2016), Christy Mackay, 20 Mar 1819; citing CREICH,SUTHERLAND,SCOTLAND, reference ; FHL microfilm 990,561.
Born 1819, and mother was a McDonald.
"Scotland Births and Baptisms, 1564-1950," database, FamilySearch(https://familysearch.org/ark:/61903/1:1:XT56-DHW : accessed 29 March 2016), Christian Mackay, 04 Apr 1813; citing Edinburgh Parish, Edinburgh, Midlothian, Scotland, reference 2:18KL3NG; FHL microfilm 1,066,688.
Christian is a girl, born 1813 - mother is a McDonald
Lots more if you extend beyond the "Donald" reference, but it could be hard to narrow it down.
Here's a couple more with Donald Mackay as father:
"Scotland Births and Baptisms, 1564-1950," database, FamilySearch(https://familysearch.org/ark:/61903/1:1:VQQT-2V5 : accessed 29 March 2016), Hector Christina Mac Kay, 04 Nov 1811; citing DURNESS,SUTHERLAND,SCOTLAND, reference ; FHL microfilm 990,562.
"Scotland Births and Baptisms, 1564-1950," database, FamilySearch(https://familysearch.org/ark:/61903/1:1:VQQ1-Z26 : accessed 29 March 2016), Christian Mac Kay, 14 Jan 1813; citing , reference ; FHL microfilm 990,580.
Good luck.