The trip north inside the Barrier Reef is one of the truly great sailing trips of the world. TI is a good, though from a provisioning point of view, expensive experience...and a terrible anchorage.There is a good, muddy bottom off Horn Island, which is a short dinghy or ferryboat ride to Engineer's Wharf on TI. Provision either in Cairns or in Darwin, which is a yacht friendly port with every imaginable service available. Darwin also has good, free anchorages (But anchor out to cope with tidal heights of around 18-20 feet.
The various rallies and races north in the middle of the year are all well worthwhile. I envy you and hope you have a wonderful, safe time.
"if at first you don't succeed....Redefine success"!