Assuming you want to spend some time in Sydney, if you fly there first, your internal clock is likely to be discombobulated, but if you arrive by ship, it should be pretty much in sync. I know it takes me a day or two…
There are currently no SYD<>HNL cruises scheduled that stop in Tahiti and Fiji.
There are cruises that start on the US west coast that have stops in Hawaii, Fiji, and Tahiti. One on Carnival this September, and one on Princess, September, 2025.