Sibling Rivalry? Just plain fighting all the time

I'm really trying to enjoy my children this summer. I wish I could say that it was going as smoothly as I'd like it to.

Right now, the 3 younger ones, 5, 7 and 9 are playing Buzz Jr. on the PS2. It's about to get shut off. All they're doing is yelling at each other. It's driving me crazy.

We can't even take a 20 minute to and from ride in the car without someone having a fit and screaming or fighting. It's insanity I tell you. I've got a headache from the stress of the day already today.