I have flown with my kids many times (even doing international flights) from them being very young and I always bring much more stuff than you ever need

My kids do not sleep well on planes, especially during night flight!
I always wipe down the tray and arms rest with wipes first

I pack each child with their own bag and they keep this with them. This way we are not passing stuff back and forth, and everyone has everything.... Especially useful on long haul.
Each child will have:
Wipes Huggies and Anti bacterial (don't ask)
Serveral snacks (crackers, goldfish)
Gum or lollipops
Colouring book/ art pad (depending on the age of the child)
Crayons or pipsqueak makers
The variables here are DS lites, ipods, leapsters and all that electrical stuff. Headphones and extra batteries for those items that need it. I also try and put the chargers with this stuff as my kids keep these bags all week and then everything is together. Any homework or journals will go in the bags and usually packs of cards, go fish and maybe a mirror or something unsual for a baby or little guy. I will also put in blankets or soft toys that the kids sleep with, so that they have there special item on the plane. I am sure I m missing stuff. One thing I will do is assemble this stuff away from the kids, it usually includes new items so they are always excited to see what they got. In the past I have kept other small new items in my bag incase it all goes south and you need an quick fix but I have to say we usually bring this stuff home for another day.
I think the key to keeping kids happy is to keep yourself calm, and try and stick to the routine they have at home. If you know you are boarding a plane and its almost breakfast time make sure you give them something to eat otherwise its not going to be fun. My kids have always known what is expected of them and I always try to do what I need to to keep them happy.
Good luck with your trip, I am sure it will be fine.