I really don't mind though, because every item I carry usually comes in handy. Also, now that the kids are older, I can sneak some things into their backpacks to share the load.
Here are 13 items I always bring whenever we catch a flight:
1. Pen & paper
Even with all the electronic devices available now, I find that a small notebook and a regular ball-point pen are must-haves when I travel. The kids can use them to play tic-tac-toe or doodle to pass the time, I can use the pen to write up some extra luggage tags before checking our suitcases, fill in customs forms, or I can write some postcards with the kids while waiting at the airport.
2. Antibacterial wipes & hand sanitizer
It's a sad fact that airplanes and airports are dirty and full of germs. Liberal use of antibacterial wipes to clean everyone's hands and also clean surfaces like tray-tables can really help keep colds, flus and stomach bugs away. A small bottle of hand-sanitizer gel always goes into my zip-loc bag of liquids too. I prefer the wipes since they don't have to go into the special bag, but the gel is a great backup.
If you've ever flown with a head-cold or sinus-infection you will know why I insist on bringing this: it is excruciatingly painful at take-off and especially when the plane is landing. I always bring a liquid decongestant for the kids, tablets for myself, plus nasal sprays for everyone, just in case we need them.
Fleece blankets are quite easy to pack into your hand-luggage if you roll them up tightly. They're great comfort items when your kids (or you!) want to sleep, snuggle or just relax on board, and they can also be rolled up and used as pillows. And if you end up stuck in an airport, they're very useful there too.
5. Kid-sized headphones
The headphones offered on-board by the airlines are usually made for adults and will probably not fit your child's head very well. It's a good idea to bring along some kid-sized headphones: they're much more comfortable for the kids when they watch any in-flight entertainment, and that in turn is much more relaxing for you because the head-phones will stay on rather than fall off every two seconds.
6. My Kindle (or books)
I used to always travel with a small supply of books. Now I travel with my Kindle, loaded with books for myself and the kids. Books in any form (paperback, hardcover, or on an e-reader or tablet) is a great way to pass the time when boredom strikes, so bring some, in whatever format you feel comfortable with.
7. A refillable water bottle
The last couple of years, I've brought along a refillable water bottle on our flights. Occasionally, I do have to empty it out before going through security, but once you're through security, you can fill it up again. Yes, you can usually get drinks on board, but it's nice to bring your own for when the kids just can't wait for a sip.
8. Chewing gum
I usually bring a fruity kind for the kids as a treat, and a minty kind for me, to help with ear-pressure and to just feel a little fresher after a long flight.
9. An address book
My tiny little blue address book has addresses and phone numbers for friends and family all over the world. I like having it along as a hard-copy in case my phone fails. The addresses also come in handy when the kids want to send postcards during our travels.
10. A clean T-shirt for myself
On long flights with my kids, accidents can and do happen, and sometimes those accidents happen on me. Spills, spit-ups (if you have a baby), smears, general dirtiness, sweat... it's just really nice to at least have the option to change into a clean shirt on board. In case of delayed flights, the clean shirt can come in very handy as a partial change of clothes as well.
11. A change of clothes for the kids
Yes, accidents can happen, even if your kids are not babies or toddlers. Because of this, I always bring one change of clothes (including socks and underwear) for each child. It's a bit of a hassle to fit into the hand-luggage, but now when the kids are older and have their own bags, they can at least carry their own change of clothes.
Luckily, I've only had to use the anti-nausea medication for my kids a couple of times over all our years of traveling. I still bring it on every flight though. A small bottle won't take up a lot of space, and if you're on a plane with a child who has an upset stomach, you will be very glad you brought this along.
13. An empty plastic bag
This easy-to-pack item can be used for wet, soiled clothes and any garbage you might get stuck with and don't know what to do with. It sounds superfluous, but comes in handy more often than you'd think.