The Globe and Mail says both sides are still negotiating with the assistance of a federal mediator, so hopefully the two sides can come to a settlement before the 21st.
But if they do strike on the 21st, I think you will be ok for the 30th. In all likelihood, the federal government will not let this last that long. I would consider writing to your MP expressing your concerns though.
I hate the idea of a trip being ruined because of AC striking (I'm hopefully flying out on Sept 29, so I'm in the same boat), but I don't think we should be writing to MPs or anything like that.
In fact, the government should technically stay out of this job action completely, since AC is no longer a Crown Corporation; it's a publicly traded (or privately owned, can't reember which) company. If some random union at a factory had issues (which happened here at Purity Factories), you wouldn't expect the government to step in and fix them. Purity was locked out for months before something was mediated.
All of that said, my trip is booked through Air Miles. I called them to ask what would happen if AC strikes, and they said I'd have to deal with AC since I didn't get the Air Miles Insurance. Air Miles would be no help at all.
I also talked to my
travel agent (who the rest of the trip is booked through), and she said not to worry too much about it right now. There are no guarantees that there will be a strike, and she said that historically when airlines strike, other airlines step up to help out so that people's vacations aren't ruined.
Finally, if you have a travel agent that you usually deal with, get in touch with them even if you didn't book through them. Like I said, I booked with Air Miles, but my TA said that if there's an issue, Air Canada usually gives TAs authority to 'take over' reservations to help make sure people get where they're going.