I travelled to Australia last year with my two little ones and trawlled the threads on here for tips to use. There were many good ones, but I did not come across this one that I heard recently so I wanted to share it.
Everyone says to wrap up presents that you get out at a rate of about 1 an hour for the little ones. This is great, but this takes it one step further. Instead of giving it direct to the child, you surrupticiously (spell) give it to a stewardess and ask them to bring it to the child when you tell them. You tell the child that on airplanes, the stewardesses give presents to the children who have sat nicely and worn their seatbelts, not made a fuss etc. Then you get them to bring the present. I think this works best for a child of about 2.5 to 4 ish. If its a short haul flight, one present to be given at the end would work well. If long haul, you would probably need a few for after strategic points - maybe after meals?
Anyway, I hope this helps someone!