Right before leaving your car (or your house if you are being taken to the airport by a car service or a family member) do a pocket/backpack check on all of the children. Make sure that they are not carrying any metal in their pockets (change, toy cars, etc.), and that they are not carrying any forbidden items in their toy bags (penknives, pointed scissors, etc.) Kids have a tendency to pick up items and put them in their pockets at the last minute.
The TSA list of items which may not be taken in carryon bags is here:
http://www.tsa.gov/public/display?theme=40&content=0900051****a91aa
(Click on the link for prohibited/permitted items)
Be prepared to remove your shoes at security. You cannot be forced to remove them unless you beep, but you'll get through much faster if you just take them off and send them through the scanner in a bin. I recommend doing the same with belts that have metal buckles. Children should not be dressed in overalls w/ metal shoulder buckles, and be wary of letting them wear zip-off trousers if the leg zippers are metal.
For pocket things that are metal but OK to carry, put a ziploc in the outer pocket of each carryon, and empty your pockets into that ziploc as soon as you arrive at the airport. Keys, sunglasses, change, wallets, all of it. Metal watches should go in, too. Then put the ziploc into your carryon, in one of the outer zipper pockets, or inside; someplace where it won't fall out. You can get the items back out and put them back after you have cleared through security.