My kids, even when teeny were OK - basically with books, inflight ent & toys they'd be happy. Even on a long flight when IFE failed they would eat, sleep and look out the windows.
Only flight one of them was a pain was a young couple behind were teasing one of ours when they were but a toddler - making the bairn excited and causing grief to calm 'em down.
The parents, not the children are oft the problem.