Canada Day is celebrated on 1st of July every year and it is a statutory holiday which means most institutions that is Government and private are closed. Usually there are penalties for private business if they are open for business on statutory holidays but I have seen some shops open though. Don't know how they get away with it.
In Toronto, for watching fireworks Woodbine beach is a pretty good place to visit but it can be crowded and packed like hell there. Take the Public Transit TTC bus to go there since you won't get parking there. Another place would be the Canada's wonderland, Nathan Philips Square (Downtown), Miliken Park (Scarborough). Most of the fireworks starts at about 10:00 PM and last for 15 to 30 Minutes.