If you forget all else, please remember this one thing- something to suck on! Nothing will be more valuable than a pacifier/bottle/sippy cup. The air pressure may not affect your child, but if it does, you'll be glad you have something for him.
A few things to play with are helpful. Preferably toys that he doesn't see everyday, so they're new and will hold his interest longer. Snacks are good, too. Between a few toys and snacks you should be able to keep him busy for an hour or so. Depending on your flight time, you might be able to get him to sleep on the long segment of your flight.
I always try to sit in the back of the plane. Passengers tend to try and get as far forward as possible, so if your flight is not crowded you may not have too many people near you. It will give you a little more room to move/stand/walk with DS, and a little space in case he is loud. Plus you don't have to rush off the plane and try not to make everyone wait because you're trying to gather everything that you stowed or played with during the flight. Generally it takes a few minutes for the ground crew to unload the strollers you checked at the gate, so it's the same amount of time if you sit in the back and walk out to a stroller waiting or sit up front and have to wait for the stroller to be unloaded. And you won't feel rushed.
Check all the bags you can. That will keep you and DH from possibly stressing over anything other than your son. We only carry on a diaper bag and backpack for things my 4yo can play with.
Those are a few things we used with DS when he was 1 and we went to WDW, and we'll be using again in a few weeks with DD who is 1. I think all infants will cry at some point, you can't avoid it. Just take what you think will work best (you know your child better than anyone) and most of all, don't rush! It's hard flying with an infant, but if you accept that and do only what you can, you will be fine. Enjoy your trip!
PS: One last thing, if he uses a pacifier, try keeping it on a string. Our first trip in 2000 a little girl must have cleared 10 rows of seats when she threw it!
