What a great idea!! Especially for kids a bit older who can regulate their activities well!!
I had a load of different things hidden away in my carryon for DD on long haul flights this summer (colouring sheets and worksheets, new story book, couple of toys wrapped up, favourite teddy and plenty of different types of snacks), and that worked very well to keep her entertained throughout the travels.
I love this idea. I just want to add that pipe cleaners are a great addition to any travel pack. This summer on a 14 hour drive to FLorida we opened a surprise every hour during our awake times. The best present by far was the pipe cleaners. We played with those for over two hours seeing what all we could create. And then they came back out several times and also on the way home.