Wea re getting ready to embark on a nine hour flight, and I'm going alone with my 3 kids...youngest being 9 months. I would recommend taking your 2 year olds car seat on the plane. When I did that last time it was so much easier. My son knew he couldn't get out, just like being in a car, and so it was easier for him to expect. I have travelled with everything but the kitchen sink and found that I was forever chasing item down. I typically find that the kids sleep more than they play, espacially if its an overnight flight, that being said this is what I pack.
* Colouring books and crayons---dollar tree is a great place
* Small puzzle in a ziplock bag
* Some snacks, but most airlines have plenty, same as juice
* Pre-book kids meals----British Airways has a policy, kids eat first!!!!
* Aqua Doodle---they have a travel size--my 7 year old loves to play with this still
Hope you have a great flight, we ar looking forward to ours. I am going to invest in a potable dvd player, but mainly for our time in England. british airways has continously running cartoon netowrk and disney channel. I have to say they are the best airline when it comes to travelling with kids.
Good luck!!!