It's a holiday weekend. There should be a lot to do. Pick up the Toronto paper (Star, Sun, even Globe & Mail) on Thursday or Friday for the entertainment guide.
If you like art and history, there's the Art Gallery of Ontario and the Royal Ontario Museum. If sports, the Toronto Blue Jays (or tour the Sky Dome if they're not playing that day or on the road). Science? Ontario Science Centre. Go visit the various neighbourhoods.....