Niagara on the Lake is an awesome little town, you can walk the main street, enjoy a bite to eat and enjoy the shops.

If you can drive from BUF, you can hit Niagara on the Lake then make your way to Toronto. Its just over an hours drive with no traffic. I would skip Niagara Falls if you have no indention of hitting a casino or a show.

Toronto has a lot to offer - CN Tower, a baseball game at the SkyDome(no,I will not call it the rogers center), museums, lots of historical buildings, shopping centers and LOTS of places to eat. All of it is very accessible via public transit and walking.