I used to fly a lot as a kid (still do as an adult!), so here are my tips!
1) If your kids are prone to motion sickness at all, watch out! Don't let them eat eggs or orange juice before the trip, don't fill them up, and DO get some Children's Dramamine! Planes hit everyone differently, but the last thing you want is a really sick kid on the plane. It ruins everyone's day.
2) All liquids, including make up, on carry-on luggage need to be put in their own see-through bag (max 1 qt) and MUST be 100ml or under. Put this somewhere you can get it quickly to make the security line go smoothly. Places like
Walmart, Target, and Walgreens sell TSA-compliant kits you can transfer liquids into.
3) Some airports ask you to take your shoes off at the security gate. Prep your kids for this eventuality and if you see others removing shoes, get started ASAP. Take off all coats, belts, and empty pockets as you approach. Trust me when I say that this takes off some stress, as no one wants to be the family holding up the security line while everyone glares.
4) I see you have a child with special needs. You might want to call your airport ahead of time to get an idea of how your security check will need to be altered for him. Knowledge of the procedure helps keep stress down on the day.
5) Popping ears on take-off or landing is hard for most kids. If yours can dive really far underwater, they'll have an idea of how to make this happen. If not, then Earplanes, as someone suggested, might help. Also, gum, eating foods, or drinking something can help, as swallowing enough often aids in ears popping (weirdly enough). Anyone particularly young might need to be prepped in the idea that their ears will need to pop.
6) You're allowed 1 "personal" luggage and one carry-on. I'd maximize this unless you plan on checking something in. Let each kid bring something to do on the plane, plus one change of clothes. Pack this in a backpack of their size to keep under the chair in front of them during the trip. Get as much as you can into carry-ons, even if it means mixing up some clothes. Keep to the size and weight restrictions, though.
7) Get to the airport early if you can. At least 2 hours should suffice. There's nothing worse than watching your flight take off without you, and the stress if that's a real possibility is HUGE. You really don't want to be angry and rushing your kids or snapping at everyone (had a lot of this when I was younger!).
8) Stay hydrated! You can get water whenever they offer drinks on the plane. If you're already feeling thirsty, ask for more than one cup the first time. They don't usually mind. Otherwise I'd bring empty water bottles to fill at a water fountain after security check.
9) If your flight is long enough to have lunch (or overlap a normal snack time), I'd include some dry snacks in my carry-on. Things that your kids like and are easy to eat and keep down are best.
10) If you're doing Magical Express, only pack in carry-ons the things that you'll need in the next 4 hours or so of landing. Place the yellow tags Disney sends on your check-in luggage prior to checking them in and go straight to the bus. Disney picks them up and delivers them for you.
And those are my two cents!