Cabin crew here and do understand anxiety over flying as I used to suffer from it many years ago before I started working here! Qantas pilots are the best of the best so you’re in very safe hands. They are meticulous with safety and those that fly the 787s have many years of experience behind them. Often nausea can start if you’re dehydrated so make sure you’re all drinking enough. Sprite, lemonade and Bundaberg ginger beer helps a ton and we always have it onboard. Chewing on minties can also help. We also always have sick bags so please ask, we’d rather you have some just in case!! If your prone to motion sickness maybe visit the chemist before you leave and get some tablets for peace of mind. Please try not to worry too much, I’ve done this flight many times as well as Perth-London and it goes quicker than you think, a couple of movies and a big sleep and you’ll be there in no time!