CN tower is a good idea. You can go there and even have dinner in one of their 2 restaurants. other then that if your interested there are normally leaf games on saturday nights, maybe you can catch one of those.
There are also a few theaters on Yonge street where you might be able to get tickets to a show. I believe We Will Rock You is at the Canon Theater Downtown Toronto. I believe tickets are on sale right now too, anywhere from 25-50 bucks.
Also if your here for Sunday you might be able to catch a Toronto Raptors game. Not sure though.
Yea I was lookin into getting tickets to the leafs game but they are sold out and stubhub the tix are way over priced so I was going to see if the hotel could get some tickets for me when I get there because sometime they actually can get them some how.