Here are a few things I would suggest going over with the kids, from my own experience.
Yes, those who get carsick are likely to get airsick, especially if there is turbulence or you end up circling due to weather. Try Bonine (meclizine), as Dramamine absolutely knocks out some kids. There are airsick bags in every seat pouch.
Talk about normal flying - the force at liftoff, bump at landing, climbs and drops, noises from landing gear/ailerons and flaps/engines, stretches of turbulence where you have to stay belted.
packing - anything you'd hate to lose (phone charger, camera, prescription) should not be in a checked bag.
dress - planes are often chilly, a long sleeved shirt over a Tshirt gives you options
backpack/totebag - for each group if seats are split up
A. time fillers - magazine, mp3, new game for the phone, 2 decks of cards, pen/paper, etc Helpful to have their own earbuds for in-flight music and videos.
B. snacks - protein bars, oatmeal cookies, cheese sticks, nuts, trail mix, crackers, licorice, anything calorie-dense to keep the kids satiated
C. bath towel - rolled up it's a pillow, unrolled it's a blanket, especially nice for very early or very late flights even for 17 year olds.
D. I carry a fast acting nasal spray in case someone has a stuffy head before flying. A plugged ear coupled with the plane's pressure changes can lead to a very painful ruptured eardrum. I've had good results with phenylephrine HCl. Check with your family doctor first if this interests you.
airport security - takes just two minutes but: shoes/belts off, personal items go in a tub for xray, liquids/gels including lip gloss go in a baggie, there's a walk thru scanner, and no joking around especially about bombs/guns/terrorists etc.
Show the kids over age seven how to read the flight monitors and figure out where you need to go.
cash - we usually give the tweens and teens $15. They can buy a magazine and snacks in the airport, or sometimes they like to try the airline's "snack box" during the flight. Let them know if pop and water are free in-flight.
toilets - Go before boarding, and on the plane go before you really need to. Aisles can be blocked for several minutes by food and beverage carts.
Check around carefully to be sure you don't leave anything behind on the plane when you disembark.
