Jerry Sandusky never appeared on MacGyver.
In the show, MacGyver often volunteered for a nonprofit organization for at-risk inner-city kids and teenagers, but it was not the Second Mile: it was the Challengers Boys and Girls Club in LA, which was simply called the Challengers Club on the show. The organization appeared in the following episodes: "The Challenge", "Runners", "The Madonna", "Tough Boys", "The Gun", and "Gunz n Boyz".
Richard Dean Anderson was active in the Challengers Boys and Girls Club as a supporter and volunteer, and is still on the Board of Trustees. As with many other aspects of the show, the writers drew on his personal interests for material and ideas.
Current website for the Challengers Boys and Girls Club: http://www.cbgcla.org/#/home/
See also: http://www.macgyveronline.com/pages/challengers.html