Sleep in. Stay in bed until at least 6:00 am.
Make everyone breakfast before you get your coffee. You don't really need it, after all, you DID sleep in.
Hop in the shower while everyone is eating. If their mouths are full they can't scream your name. Hurry up, though, somebody might need a refill.
Throw on the cleanest things you have available. Nobody's asking for perfection, it's Saturday. If you have a little time, a hairbrush and some makeup would be a nice touch.
Rush the children off to all of those activities that you signed them up for to keep THEM busy.
Upon returning home try hard to ignore their cries of "I'm bored!" Hide in the bathroom if needed.
Try to wait out the chaos. Eventually they will all settle into something they find interesting. If you're lucky, it'll be something that the whole family can share, like a movie, a TV show, a meal.
Trust me, it's worth the wait.