Not going to the CN Tower is like going to Paris and not going to the Eiffel Tower. This is such a huge landmark of the city and the views are fantastic. The best time of day would be to go about 2 hours before sunset to give you time to buy tickets and get to the top. Definitely splurge for the Skypod which gives you a nice 360 view and is less crowded. Take lots of pictures then go to Horizons which is the more casual restaurant and have some Canadian beers while watching the sunset. Then check out the city once the sun has gone down to get that pretty night view.