I used to fly with my young dc a lot. These are my top tips
A sling for walking through the airport.
One handluggage packed full of things for dc. More changes of clothes (sleepsuits) than you think youll need. Way more nappies than you think you'll need. A whole pack of wetwipes. At least 2 changes of clothes (i used maxi dresses) for yourself - that way if theres a nappy/vomit explosion or a spilt cup of water or whatever you can be clean and dry. A pashmina to use as a blanket/pillow/breastfeeding shawl/whatever.
Over the ear headphones for your dc. Download some of their favourite shows/games. Even if it just keeps them quiet for 30 minutes.
Snacks. Little things like raisins take ages to eat.
Go to the poundshop for cheap in flight toys. Teething rings, sticker books, cheap doll, whatever. Pull out a new one whenever boredom sets in.
Try and book night time flights, in the hope you'll all sleep for some of it.
I always overpack my medicine/first aid box. So in the ear thermometer, calpol, rehydration sachets, bite relief cream, hand gel, wound spray. But I'd rather overpack than underpack. Travel insurance, is a must have.
Breast (or bottle) feed on take off and landing, it helps relieve the ear pressure.