An update - I wanted to make sure to get two seats together, and did so online for the AA segments. Of course, the AC segment could not be touched.

Called the AAdvantage hotline, and used their slick voice recognition system to get to an AAgent, and my AC booking reference, within two minutes. Unfortunately, the booking number was not correct!

Called the AC Reservations line, and listened to Christmas muzak for 20 minutes. Got the correct reference number, and requested seat assignments. Unfortunately, only single seats (mostly middle) were left. The closest pair were still three rows apart.

Resigned to this, I also requested to add our Aeroplan numbers to the booking. The agent then notes "Oh, you are an Elite member. Let's see what we can do." Now with the front of the Economy cabin available, there are two seats in adjacent rows, which is a lot better than 30 seconds ago. With luck, things will open up again at check-in, or a kind passenger will accept a bulkhead seat and let me move one row back. Result!