If you are visiting Toronto of Canada, you haven't visited Niagara Falls, it means you haven't visit Toronto. Niagara Falls is on the south side of Toronto, it needs to take around one and half hour driving from Toronto city center.
My first time visiting is in 1992, it took me 4 hours to drive from the city center of Toronto to there but 2 hours to return back. It was because I was not familiar with the highway during that moment. I nearly cross the boundary to the America instead of going to Niagara Falls.
Summer time is the best season to visit, if you are not hurry to left, you should stay overnight because the lighting on the falls is very beautiful. You can have a buffet in the casino and some of them have a wide window for you enjoy the view and their foods.
I have been in both side America and Canada to see the Falls, but I found Canada side is better than America side and organization of the tourist's area is also better. Please let me know whether you are agreed with me or not after you visited both side.