Not sure if they're still open now, but at Black Creek Pioneer Village's brewery you can spend some time with the brewer and make a heritage beer. Google for their website.
Just yesterday a friend told me that Steamwhistle has a good tour - and their location is cool. They are in an old roundhouse very close to the base of the CN Tower.
I called Trafalgar Brewing in Oakville (between TO and NF) to ask about a specific beer and they seemed pretty cool on the phone and welcomed a stop-by any time, but suggested a call to make sure someone was there.
And of course, if you;re going to Niagara Falls, there are all kinds of vineyards and wineries that would be holding all kinds of events and tastings at this time of the year. Not beer, but hey, wine is good, too!