I really feel for the OP and the other Australian cruisers who are on this itinerary. The requirements have changed, and fairly recently, going from three days to two, from not proctored to proctored, and that has to be upsetting and even alarming because the instructions on the Australian Celebrity website do not match the instructions on the US Celebrity website,
I don’t know if the Optum test kits will even be mailed to Australian cruisers, and there isn’t a lot of time for this.
I agree that Celebrity will not do the testing. They have made that very clear for many itineraries now, with the possible exception being the back to back cruisers.
If you are staying in a hotel in Hawaii before the cruise, I would reach out to them for help and advice on locations that will be available to you for your pre-cruise test.