Hi
We have 2 Boys now 8 & 5. We have been flying with them both on short and long distances since the eldest was 9 months old.
We have found that it is best to ensure they are both well rested before the flight and have had sensible food and plenty of water to drink. On the flight it is vital to have a kit bag of their best games/toys/teddies to keep them amused.
Dont feel bad if the child makes a lot of noise from time to time, as others have said if you are making the effort to entertain them then most other passengers will cut you some slack.
Try to encourage the child to sleep as even a couple of hours is time that you do not have to amuse them.
Regards
Michael