iPad with various games, peppa pig etc. 19 mth dd has got into the Gruffalo, Gruffalo's child, the other one with the witch. Anyway there all about 25 minutes long and worked a treat on a recent 12 hour flight.
Stickers, crayons colour wonder good. Loads of snacks, story books you can download to iPad are good. Good app with Peppa pig magic painting and sticker scenes. Agree with the wrapping, doesn't matter what is inside, I used to use party bag type things, little crayons, notepad, pound world dolly etc.
Take iPad/DVD player with peppa pig/ night garden etc episodes downloaded on it. Take the biggest hand luggage you are allowed and fill with toys, books etc. keep bringing a new one out every 20-30 minutes. Be prepared to walk around the plane 1000 times. Stickers and colouring books are good for a bit. Bring favourite toy/ sleeping bag/ blanket from home so naps are easier.