It is daunting thinking about travelling with a toddler but I have found the thought worse than the reality.
I always ask for a bassinet, even though my kids have been too big for them at the time of travel. But it gives u heaps more leg space (where DS can play) and you can store your toys in the bassinet!
I recently took pegs on our flight, and they entertained DD for hours!!!!! I would peg them on her shirt and she would pull them off, or peg the blanket they give u to make a little house etc. who would have thought?! (and they came in really handy on our trip for washing and pegging curtains together that were letting too much light in at rest time!!)
I bought a cheap magna doodle which was a hit and a big motor bike that zoomed along every seat on the plane.
My advice would be; don't let ds roam the isles until you are desperate. Once you start he won't want to stop.
Good luck! You will survive.