Don't be deceived by the map in post #28. It looks like the cruise ship terminal is right next to the airport. You can actually see parked planes close by. Unfortunately, to get to the terminal building from the BICT, you would have to drive across the runways. The road route goes around three sides of a square, and is about 12 kms. When I took the shuttle bus organised by the cruise line, it dropped us off a five minute walk from the terminal building. I'd allow 30 minutes from the port to airport check in.
www.google.com.au/maps/dir/Brisbane+International+Cruise+Terminal+-+BICT,+1+Cruise+Terminal+Dr,+Pinkenba+QLD+4008/Brisbane+Airport+(BNE),+Airport+Dr,+Brisbane+Airport+QLD
If you have lots of luggage, make sure you buy some extra luggage allowance in advance. Buying it at check in is very expensive. Also check the size/weight restrictions, which are stricter in Australia.