J.M.
I travel often with my 2 year old. If you can afford it, get a seat for your son. It gives him his own space and quite frankly you a break too. You'll have to take a car seat with you though. www.onestepahead.com has a couple of options to carry the car seat. There's a backpack and a rolling cover. Also, if he's over 22 lbs. the FAA just approved a new restraining device that only weighs a pound. You can get it at www.kidsflysafe.org. It's about $75, but can be used up to 40 lbs. It's called the CARES device. We used it on our last trip and it was a life (and back) saver! Also, a portable DVD player works great. We don't do too much TV at home, so on the plane it's a special treat for my daughter and she just LOVES it and stays calm for most of the flight. I've found toys and books are tough because they end up all over the floor and it's hard to bend over to search for them. Good Luck.