Domestic Flights in Australia and Transfers

We'll be going on an Australia/NZ cruise out of Sydney next year. Our plan is to do pre-cruise time in Sydney, then fly to Cairns post-cruise to dive the GBR. We then plan on booking our flights home to the US from Cairns so we can do it in one day (we'll have a stop over in Sydney that will allow us to stretch our legs a bit). We'll get AUD when we arrive in Sydney, and hopefully some NZD once we get to our first shore stop.

We plan on booking the domestic flight out of Sydney to Cairns at 2:15 to make sure we show up on time after our Princess Cruise. It looks like Princess recommends not booking flights before 12:15. My first question is, if we get to the airport ridiculously early for the 2:15 flight, and Qantas has an earlier flight, would they let us change to the earlier flight. We've decided we would rather spend some time at the airport rather than rush to get there. We don't want to use option of taking our own luggage off as our traveling companions both have some shoulder issues and we don't want them to have to wrestle with their luggage more than they have to.

Second question is, will the domestic luggage allowance on Qantas be the same as the international allowance?

Third question, knowing that cruise line transfers tend to be pricey, is there another option (keeping our friends' shoulder issues in mind) that would get the 4 of us from the pier to the airport at a better cost?

Regarding changing to the earlier flight, they won't normally do that (unless you pay change fees!) so not something to expect.

For luggage allowance, it sounds like a separate ticket for the domestic one. As such, it will be the standard domestic allowance. Fortunately with Qantas that is more than the other domestic airlines (though Virgin recently changed), but as you're coming from the US I don't think it will be quite as much as you have for the international flight. I know those US flights used to be higher, though not sure what QF offer now for the US.

As you're on Princess, you're probably coming into White Bay. In that case, a taxi will be cheaper than the transfer, for 4 of you. However, there would likely be a wait for one although they do come to the terminal. The difference is probably about $30 US in total for the 4 of you, so your call as to whether that's worth the saving.

Question 1: Qantas might allow you to change to an earlier flight. It all depends on the kind of fare you purchased. If you are allowed to make a change, you most likely will have to pay the difference in the fare you purchased and that day's current fare. It's all somewhat complicated, but you can find the info here: http://www.qantas.com.au/regions/amadeus/minirules/AUAURED1JQ_SUMMARY/

(The bottom line is that it's probably not going to be worth the extra cost IF you can even do it.)

2. The domestic luggage allowance on Qantas is 1 piece of checked luggage plus one piece of carry-on luggage. Here are the restrictions on weight and size for both types:

http://www.qantas.com.au/travel/airlines/checked-baggage/global/en#domestic-flights

http://www.qantas.com.au/travel/airlines/carry-on-baggage/global/en#carry-on-baggage-allowances

3. According to TaxiFareFinder, the cost of a taxi between White Bay Cruise Terminal and the Sydney airport is around A$55. That's got to be less than what the cruiseline will charge for 4 transfers.