Hi Mark,
Hope you enjoy your stay in Cairns..I will be there all week from Sun 13th Oct to Fri 18th. make sure you get a convertible from Hertz or Avis and do the drive to Port Douglas. Also, for the best reef trip, try Quicksilver out of Cairns (or Port ) You should also try eating at "red ochre" a real treat for native food. (Kangaroo, emu & buffalo") Seafood is great and I can suggest you try "sails" in Port Douglas for some great food as well.
Hope you enjoy your time in Queensland.
Iain