OK I know they will mainly watch their devices or the in flight entertainment but when I was little and my mum took us home to her home country (8-10 hour flight) she used to produce new toys every so often - I distinctly remember my Fisher Price Little People being produced on a plane.
I am thinking of travel games, a lunch box (DS has some SEN and can be a slightly fussy eater so this might work if he won't eat the plane meal too), a book each. I am also aware it might get very heavy if I don't cut down the size especially if I want to produce more than 2 or 3 things each.
DS will probably reject anything we produce except a new Bunny vs Monkey book and several bags of Skittles, but I'm going to try a Where's Wally book and travel Snakes and Ladders.