R.W.
Hi J.,
I'm sorry to say I don't really have any great advice for you, but if it helps any, I know just how you feel. I also have five kids, ages 8, 7, 5, 5 and 4. Only my two oldest are invovled in any activities right now, and it's all ready crazy. I can hardly imagine what it's going to be like in a few years when they're all in scouts, sports, etc.
One simple thing we do that seems to help a bit is having them start their homework in the car on the way home from school. It's only a 10 minute drive, but it does help! Then when we get home, they're all ready in the groove and end up finishing their homework right away, instead of stalling to even get it started.
Best of luck to you!
R.