My wife and I visited Niagara Falls in 1989, so I can tell you something of our experience. We were on the USA side only, and we had an interesting time, but it was obvious to us that the best view of the falls is from the Canada side. We had a rented car, but we didn't go into Canada. Anyway, this is what we did, and you might care to put these experiences on your list.
1. Helicopter flight over the falls. Recommended. Take a good camera.
2. Visit to folk art museum in Niagara town. Watched native dances, which included a dancer passing one of his legs through the flame from some kind of burner. Very interesting.
3. Sailed right up to, and through the spray, of falls in Maid of the Mist. Recommended.You are given a rain cape (full length, with a hood) under which you should hold your camera whilst sailing through the mist. Wear footwear that will stand getting wet (or take your shoes off on the boat) because the cape won't protect your feet.
4. Went right up to the base of the falls, on river bank footpath. That was called "The Cave of the Winds" visit. There was a wooden "bridge", called the Hurricane Deck, which allows you to get really close (and wet) to some of the smaller, side falls (not the main ones). You are given a rain cape, plus you wear "shoes" made of carpeting, tied on with tapes, and leave your proper footwear in a locker room. Recommended.
NB. We did all that in one day, and all on the USA side, but we went just before the season started, so you should allow at least two days for a Niagara Falls visit. I hope that you have a good time.