when i brought my ds1 overseas when he was 3, i brought along titbits and sweets for him to munch on. also, the inflight entertainment and meals is enough to distract him. for some kids, their ear may hurt when the plane rise up in the atmosphere, so you can give them a sweet to suck when the plane takes off..to relief the pressure in the eardrum.
we separate him with my nephew, so as to reduce the interactions on the plane - less interactions, less likehood of quarrelling.
to curb morning rush, you can either wake up earlier, or you pack your stuff the night before.
also be prepared to stay back in the bus while others tour (ie forgoing certain small parts of the trip), cos kids sometimes will throw tantrums. in such case, you can split up ie one parent remain, and one parent take the other kid to join the tour, or both parent remain, and you need to have some activities (drawing, games, toys) for the unaffected kid while you attend to the tantrum one.
also, do bring along medication...you dont't want to scout Australia in the middle of the night in case you kid is sick (touch wood).
enjoy your trip.