OK, there is one big thing here (which I think I've told you about elsewhere). Because you're mostly flying on AA flight numbers and the booking class is O, you will earn no Qantas Frequent Flyer miles or status credits for them (even on the flights that are actually operated by Qantas) - source here. If you want to earn miles etc you will have to credit the flights somewhere else, although some other schemes also exclude AA O class from earning. In any case, if you do that you run the risk of ending up with a few thousand orphan miles in another scheme which are difficult to use on their own, which could be just as useless.

One obvious possibility is putting these flights into the AA scheme. But you'd only have something like 20,000, which could be difficult to use.

Another alternative is to put them into the BA scheme. It may only be 20,000, but the BA scheme can be good for redeeming on short flights where the mileage requirement can be very low - as low as 4,500 per one-way flight. However, you can't join the BA scheme with an Australian address.

So another alternative you should think about is booking the same flights but using QF flight numbers. Then they will earn in the QF scheme. However, what is the extra cost? Is 20,000 or so miles worth that much money to you?

I know this is a complication that you probably don't want at this stage, but I think it's better that you should be fully aware now than be surprised and disappointed later.

If you decide to book the AA flight numbers but haven't decided which frequent flyer scheme to put the miles into, then just leave that blank at the moment. Do NOT put in your QF frequent flyer number. Once a frequent flyer number goes in, it can get very "sticky" even if you want to change it later, and you can end up with avoidable hassles trying to get the miles to go to the right place.

As I said before, don't forget you should be able to get lounge access at SYD when you're finally flying SYD-ADL if you do it on QF, if it's still within your membership period.