Other than food you should probably pack more toys if he decides to stay up during the flight and need some form of entertainment. Whatever that can distract him would be useful. Remember his security blanket if he has one. Probably a pacifier just in case even though he doesn't use it? An iPad can also help save the day. Yes we are all aware of the implications, but when you're stuck on the plane with a crying baby, you will thank Steve Jobs for it.
You can request for baby food onboard or get the stewardess for some warm water for milk. If you are afraid that baby might cause disturbance to other passengers, maybe you can pack some small snacks for the passengers around you? http://sg.theasianparent.com/how-to-trick-children-into-surviving-an-airplane-ride-the-guide/
thanks