Hi there, I have taken dd to Australia a couple of times, and the flight was never as bad as I thought it was going to be. To be fair I only had 1, but she was a little handful, and I did dread it! Also had a rather unhelpful husband, who was sometimes more trouble than little dd
I took her favourite toys with her, but also took some new toys. As she's been older, I have wrapped them up and made it a real occasion, and she has to sit quietly or whatever for so long until she got one. That worked a treat for her (she is 4 btw, and this worked since she was 2.5). Took plenty of little snacks so that I wasn't dependant on the stewardesses, as we all know how immediately a toddler needs something! Last time we flew I got her some of the Crayola colour wonder stuff, and she loved it, played with it for ages, and it's mess free, light to pack etc, so I'd recommend that.
Most of the airlines have great facilities for kids on the personal tv's, so she was able to watch a couple of her favourite shows, a bit of a movie, try to play the computer games. When I first took her to Oz she was 7 months, and so stayed in the sky cot (make sure you get one) or on the boob most of the time. She also liked to be bounced, but walking up and down the aisles was fine, and nobody seemed to mind.
Might be worth having a bottle of meds with you too?! Used phenergan one time on a night flight, and she slept as soon as we got on the plane until we began our descent into Singapore!! Remember that as it's such a long flight, the children are BOUND to sleep some of it. It really wasn't that bad in the end, and like you say, it's definitely worth it when you get there. Good luck and happy holiday!