MacKinnon has been an assistant coach with the Gee-Gees since the start of the 2008-09 season. An Ottawa native and full-time teacher at Ashbury College, MacKinnon worked for many years alongside Sparks, coaching the Ashbury College women's basketball team and currently the varsity boys’ basketball team. He has coached both high school and OBA club and development teams for the past 25 years.
From 1975 to 1984, MacKinnon was a dominant athlete in the Ottawa area, playing lacrosse, hockey and basketball at the high school and club level.
He holds a bachelor of Physical Education and Mathematics from the University of Ottawa, as well as a bachelor of Education from Queen's.
Presently, he is a physical education and mathematics teacher at Ashbury College and the athletic director of the Junior School.