Rod,
Curious as to what makes you think this could be Angus' family?
However, I see from the Census they were listed as both being Catholic so they would have been buried in a Catholic Cemetery see below. Have you ever contacted them regarding Angus? You might get lucky and his father's name or his birthplace is on the stone or in their records.
Name Sarah McLean
Date of Burial 25 April 1896
Source pre-1906 Death Index. R. C. Church, Cardigan Bridge, Book 1
Notes R. C. Cemetery, Cardigan Bridge. Nee: MacGillivray
Then there is the local newspaper
http://www.caimbeul.org/newsitems/pei_news_intro.html it covers the years but I am unsure if it is complete.
Then the fine folks at the peigs (peigs.ca), and Island Register.
Good luck with your search.
Don