My tips for traveling on planes with children:
*Plan on being delayed. Take extra food, drinks, and diapers as appropriate and plan on taking an extra 6-12 hours to arrive at your destination beyond what is scheduled. I am always sad to see the mothers at the airports on the news who have run out of diapers, formula, etc., for their small children during blizzards and thunderstorms. My carry-ons have always been stuffed with extra food (I've even fed flight attendants during delays). Food entertains and fills tummys.
*Take lots of "new" things. We keep a stash of sticker books, coloring books, and other smaller/flatter items to take on our trips. It provides something new for the kid(s) to play with and is relatively quiet for those seated nearby. Costco is a great resource for such items, and Target has a nice supply of "workbooks" my daughter enjoys.
*If you have a laptop with a DVD drive, you are in great shape. Either buy some new DVDs on eBay, or check them out from your local library, or from Netflix, and go to town.
*Bring whatever comfort items your child needs at nap/bedtime. My daughter often will cuddle her blankie and stuffed friends while sitting on the plane even if she isn't really going to sleep. They are relatively small and lightweight, and in my case are critical if we ever get stuck somewhere overnight without our checked luggage.
*When packing, think about not seeing your checked luggage for 24-48 hours. Take a spare set of clothes/underwear/etc. for everyone involved plus whatever else you would want overnight (comfort items, diapers, etc.). This is especially true if you are making a connection and could get stuck at someplace that is neither your destination nor your starting point.
*Seriously consider buying a seat for all children, even those under two. It gives you a lot more space, and is signficantly safer. Take your carseat for kids under 40 lbs on the plane--another familiar item.
*Make sure it seems like fun. Let your kids explore the cockpit if possible--my daughter has sat in several pilot's seats and asks them all sorts of questions and they are almost always very agreeable and friendly. Wander the plane partway through with tiny kids (<4) just to get up and move around. Get a window seat and look at the other planes taking off and landing, and point out things on the ground below while in flight.