OK...hope I can help.
1. The Kiosks (there are a whole bunch of them) are just to the left or the "regular" counter for Air Canada
2. Yes, we had pre selected seats (I think most Air Canada flights do) and we used this service
3. I doubt you'll screw up. If you do, you are 2 or 3 feet from the baggage check in, and they could help you. In fact our situation was a little wierd, because I had one e-ticket for 4 members of our family and the 5th family member was on her own tickety. We ended up checking the 4 in at the Kiosk...than proceeded to the baggage counter, and they checked in the 5th member there. No problems with this, and no hassle either.
4. Once you use the Kiosk, walk approximately 3 feet foreward, and you'll check your bags here.
5. There are many Kiosks, and we went to one with no line at all. (Even if there were a little line, it would be quicker than the usual way)
6. I think it might take you 5 minutes at the Kiosk, and 5 to 10 min at the baggage counter. (The baggage counter is where you show your ID)
7. Stroller/ Car Seat would not be any more of a problem than going to the regular line.
8. We too had a 10:15 flight. We got to the Airport at 7:00 and really, that was too early. (We wanted to go early as we had to drive form Barrie, and you never know how the morning commute will go). So, I definately think that 7:30 is more than enough time. We were a little worried since 9/11 that it would take a long time to get through security, but after our trip down we saw that 2 hours really was enough, so on our trip back to Canada, we got to the Orlando ariport just 2 hours early, and that was plenty of time.
HTH
Karen