We had a long flight with DS and DD when they were 4 and 2.
I packed them a special backpack with-
mini stuffed animals
paper and crayons
candy (for if I got desperate!)
The toys were all new and wrapped up. I got things as cheap as I could at Target. I also strongly suggested they nap at one point.
When I got on, I got the LOOK from people since I had two DC.
When I got off, I got tons of compliments on my great kids. They had even entertained some older ladies next to us by singing little songs. It want great, but it could have easily went the other way! I am not looking forward to doing it again anytime soon.