This is a really excellent tipsheet:
http://flyingwithchildren.blogspot.com/
Pack minimally for what you need on the flight, and check everything else. Make sure you pack for a quick trip through security. I keep all our liquids (mine and kiddos) in one ziploc baggie--includes small travel-sized kit of everything we need for 24 hours (in case of travel delays or lost luggage). So in addition to my toothpaste/moisturizer/other toiletries, you might add a bottle of baby motrin and some diaper cream. Pack this into an exterior pocket or on the top. If you have liquid foods/snacks, pack them into a second (can be bigger than quart) ziploc. I keep an empty sippy cup in there too, and fill it after security.
Totally agree with the ziplocs-for-everything idea. One is your diaper-changing pack; another for a full change of clothes; one more for snacks; another for a clean shirt and undies for yourself. I always brought a water bottle with a sport top and an e-reader for myself--the key to both of these is that if your kid falls asleep on you, you can operate them with one hand (maybe not such an issue if you have another seat, though--we always traveled with my son as a lap child).
Snack catcher can be an excellent and novel new "toy." Apps on your phone. Blanket for peekaboo. The barf bag (you put stuff in!! you take stuff out!!). Pictures on your phone of the people you are going to visit.