Hi!
We recently traveled with our 3 children (8,6,4) to California (yeah for Disney!!).
-You can take snacks and they do not have to be in a ziplock (like makeup, etc) and you do not have to pull them out of the bag. I had granola bars, fruit snacks and candy treats. I found that it was easiest to have one carry-on that I carried (Dad had his own). It had snacks, book for each, Ipad, Ipod, color book and color crayons (in a ziplock only in case they spilled everywhere). They key is to try to stay organized :) Each child carried their own "lovey" which was placed in the bin through security (my daughter's had batteries (talking doll) and it was fine.)
-You cannot take any drink (or baby food) through security but you could take an empty sippy and fill it up once you get through security. There are lots of places to buy drinks "on the other side"...
-You will need to put your entire carryon in one of those bins (unless it's the larger w/wheels carry-on). It's nice having everything all together since the adults have to take off shoes, belts, and everyone - coats. You can stuff it all in one or five bins if needed. They will scan it and will only look at it if something is suspicious.
-Kids 12 and younger no longer have to take their shoes off (yeah!!). I would suggest to have them take off coats or sweatshirts before it's your turn in line. Put up the bin, have everyone put their stuff inside, have mom or dad go through the detector first, have one child follow at a time and the other parent go through last.
We also chose to carry-on the younger two's booster seats. They fit right at our feet and it was one less thing to check (and pay for). But if your carseat is bigger, you can buy carseat bags and check it. We have done this before and it's a great place to stuff extra blankets, toys, etc.
It's really not stressful and a very smooth process. If you have ID cards for the kids that's helpful but I don't think it's required (we took their passports and they did look at them and asked the kids their names (mine are 8, 6, 4).)
Just remember to take your time. There is always someone in a hurry but that is not your fault. Give yourself plenty of time and have fun on your trip!! :0)