We just bought Leap Frog Tags for our girls. They are so cool! I am not a fan of "plugging in" your children- but these are not video games so I feel a little better about them.
I like them for two reasons- you can use them with headphones- and they utilize real children's literature and not just cartoon character stories.
They were great on the plane and didn't take up much carry-on space. They entertained both my 3 and 5 y/o.
We also brought along color wonder markers, finger paints and workbooks. The finger paints were fun- and only showed up on the paper- so no mess.
My younger daughter enjoyed a new set of Little Mermaid plastic characters and my older daughter loved all the snacks we packed that she doesn't normally get to eat. I.e. fruit snacks and Pringles chips.
Enjoy the trip!
I just googled it, it does look really cool! He also has a Whiz kid learning system, but i thought it might be kinda big to bring along, plus each page is separate. He's not really into it either, loses interest after a minute or so. Plus i'm not sure if it uses headphones.