Some other things:
1. Go to Goat Island (NY State Park). You can park for free on the street opposite the bridge to the island. Then walk to Luna Island and you'll be able to look straight down the falls. The Cave of the Winds is on Goat island.
2. My favorite place on the Canada side is the Niagara Glen. It's on the Niagara Parkway across from the golf course and north of the Spanish Aero Car. There is a parking lot and a picnic area. You can get a map at the restaurant/shop on the river side. Then walk down the big step of stairs to the paths in the Glen. It is beautiful in there and at the bottom you are right up against the Niagara River Rapids. It is the most dangerous natural white water class and you get a real feeling for the river and its power.The fall colors will be at their peak.
These are some of the things I would have liked to do if I had more time!
Is the Niagara Parkway open during winter? Or are the stairs too icy and are shut?