To be honest, there isn't much to do there... On the American side, there is pretty much nothing to do. You can visit the park, walk along the falls, that's about it. You can also go to Seneca Niagara Casino, if you're into gambling.
The Canadian side is better, but still nothing great. There are 2 casinos, and random things to do on Clifton Hill/Victoria Ave. Honestly, I'd have a hard time trying to fill 3 days of stuff to do there. If you weren't with your mom, I would suggest going to Sundowners (strip club). Maybe go to Marine Land? There is also an outlet mall you can check out near the Canadian side.
dissenting opinion:
Canadian side = tourist trap with a view of the falls
American side = national park
We flew into Buffalo and went to Niagara (American side). Spent a few hours walking around - you can do considerably more walking on the American side. Treat it like a national park - it's a decent hike to do the full loop.
DO go on the Maid of the Mist tour. It's not that expensive and it brings you real close to the falls. The water is so intense that I had a hard time breathing while going through the horseshoe falls. You WILL get wet. The tour departs on both the American and Canadian side - the American side is MUCH cleaner. All the shit from the water gets pushed to the Canadian side.
After a few hours on the American side, we walked the rainbow bridge to the Canadian side. No fee to go to CAN, but its' like 50 cents to go back to the US. Bring your passport.
Once we got to the Canadian side, we spent like 45 minutes there. We got over it, real quick. Srsly man, it's a fucking tourist trap with a hard rock cafe and a casino.
So in conclusion, if you want pretty lights sounds and noise, go to the Canadian side. If you want serene national park, go to the American side.
Niagara Falls = 1 day trip. If you got multiple days, I'd go to Toronto as well.