I would put in a variety of things he plays with during the day. Probably matchbox cars, maybe one favorite and one new. Stickers are fun with a sticker book as you can stick and re-stick like colorforms. My sil hits up the FF restaurants before a trip for the toys and toddler toys, they let her purchase them without the meal. My dd's love pipe cleaners and wikki sticks but they may not be appropriate for younger kids. You never know what will keep their attention, my dd once played with a roll of scotch tape for an entire 2 hour trip.
I would bring a sippy cup and then purchase drinks after you clear security. This way you have what you need/want and won't hve to wait for the FA if things get busy. New and different snacks are great - things you wouldn't give him at home like gummy snacks, starburst or lolly pops can be fun and help with ear popping.
I would also suggest putting his things in his bag and then inside yours for most of the trip. I find the less to keep track of the better especially getting through security. Then when you get on the airplane you can bring out his bag.
Lastly, I am requesting folks think twice about bringing playdoh onboard for kids to play with. It smells and its messy - and there are so many great alternatives. Remember that although you may be going on vacation many travelers are not so lucky. My dh travels for business and often heads to a meeting right from (or at) the airport with no time to change. Playdoh is very oily and I find it difficult to clean up after in the best circumstances so imagine the mess it can make onboard the aircraft?
TJ
