Children headphones
Children's tablet
Great for plane seats if you Child's nappy leaks a lot
Keep their feet warm while flying but comfy not squashed in shoes
Children water bottle
My kid still lives these will play for hours with them
Take off and landing chewing can help relief the pressure
Any spoiled clothing or dirty nappies can be thrown in a wet bag
Travel pram can come in super handy. See if you can attach bags to it to save carrying those.
Suitcase with wheels where it stands ups can be good as the kid can sit on top.
Another great option is a ride on suitcase. If it's small enough for cabin luggage then you can take it right up to the plane
To help prevent little ones running off
If you get stuck with your child in a store, have a new exciting toy to encourage them to walk away.
Cooler bag to store snacks and milk bottles
Bottles that don't leak