Qantas Club checked baggage allowance question

I'm flying from DFW (Dallas, Texas, USA) to MEL (Melbourne, Victoria, Australia)

I'm currently travelling Economy Class, which allows one checked bag (up to 30kg).

I'm going to be bringing two additional checked bags back with me (all will be slightly less than 30kg), three in total.

If I paid ahead of time for the two additional checked bags it would cost me $300USD, which I haven't done yet.

I've put a bid in to upgrade from Economy Class to Business Class, but I don't think I will know if that was successful until probably the day of the flight.

If I'm successful with this Business Class upgrade bid, then I would only need to pay $150USD for one additional checked bag, as Business Class allows two checked bags.

Qantas Club members are allowed three checked bags (up to 30kg).

The question I have is if I discover that my Business Class upgrade bid is unsuccessful, could I then pay the $228USD to join Qantas Club, and be allowed to have my three checked bags, even though I didn't identify myself as a Qantas Club member at the time of booking my ticket?

I hope that all makes sense :-)

Thanks for any help anyone can provide.