@Eventhorizon
I've traveled with my kitties on planes before back and forth between LA and Chicago. I hope what I can share can be of some value to you.
My first time doing this was when I only had one kitty, and she was very skittish even on a good day. She trusted only me, so of course I wanted her in the cabin with me. I was young and stupid and vastly unaware of the technicalities of traveling with a "carry-on" pet and had to scramble last minute to get everything done. I'm sure you're already doing your research on this, as evidenced by this thread, but here you go anyway.
•The airline needed a vet check that she was ok to travel and was in good health, no communicable diseases, etc. in order to be in the cabin of the plane. I had to present this paperwork upon check in and again before boarding.
•Airline security will require you to remove her from her carrier, place the carrier through xray, and while holding her, walk through the metal detector/ scanner or whatever security measures your airport has. Easier said than done with people clamoring about that will frighten her. Since my girl was skittish anyway, I bought a harness to securely and safely hold her amidst all those people taking their shoes off, the beeping of the security wands and scanners, and just the general elevated noise that comes when so many people are in a single place.
•Consider having a vet give her a mild sedative before the flight to help keep her calm during security check in and the flight itself.
•Pack baby wipes for any accidents, and being along a small plastic bowl so you can get bottled water from the attendants. Also, a small towel or blanket that has both your scents on it (sleep with it a couple days) to place in her carrier will help to soothe her.
•When you're able to move about the cabin, ask the attendants of it'll be ok if she sits in your lap. I was able to keep my hand in the carrier to pet and comfort her the entire trip.
I'll let you know if anything else comes to mind. And congrats!