With little kids, I'd hesitate to have them each have their own bag. Getting through security is stressful and I've always found that having less stuff to lug around (and keep track of) is better when trying to get through the airport, security, and onto the plane.
The kids will not have to take their shoes off, so that's one less thing to worry about. If you have a stroller with you, it will need to be folded to go through the xray machine. I forgot about this once. DH went through first, then DD7 and DS5. I found myself with bags, a baby in a carseat/stroller travel system and no help. The TSA agent held DS (5 mos old) so I could take the car seat off the stroller and fold the stroller.