As usual, I’m in complete agreement with Katisha’s Shakespearean criticism. I liked Henry VI - Revenge in France, thought Henry VI - Revolt in England, was even better, and found Tom McCamus the most fussy and unfrightening Richard III possible. My image of Richard III can be summarised by one of our esteemed Dopers’ sig: “It’s called evil, kid.” Evil. Not fussiness. The actor playing the young Richard III in Henry VI - Revolt in England got it right. He was smart, and evil, and having a blast. Unfortunately, that simple vision didn’t carry through to the staging of Richard III.
We also saw Threepenny Opera, starring McCamus as MacHeath. Unrelievedly gloomy staging, punctuated by outbreaks of Wagnerian Marxism. I’ve never seen it before, but friends have seen it in different stagings and tell me it’s good. I’m not convinced.
My Fair Lady was fun and frivolous, but if you’ve seen the movie, you’ve already got a good idea what it’s like.
The best of the lot was Brian Bedford’s one man show on Shakespeare, The Lunatic, the Lover and the Poet. It was marred somewhat by the fact that the Beloved and I ended up sitting next to half a dozen little old ladies from New York who were there because this is culture, dammit! Loud mutterings from them about these Canadian actors who mumble and refuse to use mikes, “so you won’t be able to hear them very well, dear.” One was a gum-cracker, another fell asleep and started to snore, while a third chirped in when Bedford began the ‘Tomorrow and tomorrow’ speech from the Scots play. It was evidently a favourite piece for her, as she began to recite it along with him, in a carrying voice. She also was going faster than him, so it was polyphony, rather than stereo.
Once I started to think of them as groundlings, I managed to get past it. (Until one of them farted at us as we were filing out.)
But all of that is a bit of a side issue. With respect to your questions, if you’re staying within southern Ontario and Quebec (i.e. - what’s called the Windsor-Quebec corridor), you’ll find VIA pretty reliable. It’s how I got around when I was a student in Ontario and Quebec. Last time I used it was two years ago, and I booked my tickets on the Via Rail webpage, which worked fine. I would recommend booking your tickets a few days in advance, but I’ve never been unable to get a ride on VIA, even on short notice - the only difficulty is that on short notice, you may not get the departure time you want, which may make connexions difficult.
I don’t know if VIA would run to Niagra/Niagra-on-the Lake, so you may have to switch to a bus. I would recommend both, but preferred Niagra-on-the-Lake - you could squeeze in some Shaw, and present the ticket stubs to your committee as further proof of the educational nature of your trip. 
Ottawa and Quebec City are two of my favourite Central Canadian destinations - highly recommended. Two attractions in Ottawa that I always enjoy are the East Block, with the original offices of the early Prime Ministers and the first Cabinet room (although I think it’s only open weekends and holidays) and Laurier House, former private residence of Prime Ministers Laurier and King. You can go from T.O. to Ottawa by VIA, and from Ottawa to Quebec City.
As for clothing - last time we were there in September, there was a heat wave and we were wearing shorts and t-shirts. Other times, especially at Quebec City, you can get dramatic cold fronts, and need jeans, sweaters, and light jackets in September - typical “New England fall” type weather. In short - highly unpredictable (but snow is unlikely.
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