I've got both the QF and AA record locators and I'm using the relevant locator reference depending on who I am talking to (QF or AA call centre).Just to second that, I had a internal AA flight booked through the QF website and the AA Twitter team were very prompt in giving me my AA book reference, and did the seat selection on the spot for me.
Edit: see if AA can provide your QANTAS booking record locator.
I've tweeted both Qantas and AA and both have given me the same response - the seat map is restricted and we'll have to wait til we get to the airport. Which is not ideal because we want to sit together since we're travelling alone with our kids.
The best Qantas Twitter could do was put a note on our booking saying we want these specific seats.
Our flight into LA arrives 4 hours before the LAX-SYD flight so I guess we can only hope that it's enough time to get our preferred seats.
*sigh* it's incredibly annoying and frustrating.