Just off the top of my head:
 
Ontario Science Center is a great way to spend a few  hours
Toronto Harbor Cruise (great view of some old Toronto history)
Ontario Place (down in the west end of the harbor)
 
Any of these would be a great way to spend some or all of a Saturday in TO.
 
I wish I could be there rather than playing in Buffalo - ah well, there's
always
Monday onwards!
See y'all
Tony