kinglobjaw - it is not standby. You have a ticket. Once you get to the airport to check-in Qantas can take control of the ticket and open up space so long as there are seats available on the flight. You could go to the airport 24 hours in advance to check-in.
Another suggestion: get AA to conference call with QF. Gary of VFTW did this to get an infant ticket issued.
The Strange Way to Ticket Infant Travel on Qantas When Redeeming American Miles (How I Saved $1800 Traveling With My Daughter)
I rang up Qantas and was told American had to do it. I rang up Qantas again and was again told that American had to do it.
I finally got American Airlines back, confirming that they could not and the correct procedure was for Qantas to do it. Since I couldn’t find an agent at Qantas willing to do it (frustratingly calls to Qantas meant about 20 minute hold times each time) I needed to get creative. That meant conferencing American Airlines in with Qantas. Together they figured out that yes — Qantas needed to do it — and it was possible.
This meant finding a Qantas agent willing to talk to a supervisor, and finding a supervisor familiar with the process.