I was a cloth diaper user so your tip makes sense... I always did that even for local trips/ errands. Each wet bag (just like a cloth ziplock) packed with a wipe, and diaper. Then I could toss the dirty right in the bag so no smells for me or anyone else.
Love the idea to put essentials in a baggie in the pocket. I kept some in my mini purse and pulled in out of the diaper bag and tucked it next to me. That sounds even better. Esp to have a bag for everyone.
Not just for the airplane but we save the straw cups from restaurants (Olive Garden, Applebee's, Red Robin, etc) I know fewer places use these now. Booo. Anyway, they are light and easy to carry, stackable, and contain juice in case of spills. And even big kids can use them. No worries about tossing one. I put my airplane juice in an empty water bottle.
Carry lollies for kids too young for gum. Keep the kids' Tylenol or Motrin handy in case their ears do hurt or other travel related event (I tend to get headaches when I fly) I've never needed the kids Tylenol but I remember a trip with a baby who was obviously uncomfortable and crying. Not a cranky-no-nap-bored-cry, an in-pain-cry.
If you take a carseat remember rubber bands to wrap up all the extra straps you won't need on the plane. Easier to carry that way. Stuff a light blanket or other small essentials under the seat padding to carry and board.
If the seat has a cupholder, use it to hold crayons (kept in a plastic cup with a lid- old abandoned sippy cups work well)
Early AM trip? Put your kid to bed in comfy clothes. My toddler wore a loose dress last year to bed and to travel. We brushed her hair and teeth after we checked in at the airport.
Know that strollers need to be folded at security.
Have your camera available for shots on the kids in travel.

Driving- practice packing your car so the front-seat passenger can reach everything. We use a basket with compartments. A cooler fits nicely in most cars on the back seat floor if the kids' feet don't reach anyway.
Bring out new toys or old toys that you've put away for a while.
Crayons melt in hot cars.
Window markers and clings are fun.
An old training potty might be useful along the highway
