Always pack an extra 1-2 quarts more than the outing requires. More than once we've had scouts go down when they were dehydrated, or temps were higher than expected.

The 10 E's covers most of what you need. Just beef up the FAK as you have, with kid doses of meds. I'd be leary about handing out meds if you don't have permission slips, though, with today's culture.

An extra beanie, gloves, a few AA batteries. Invariably there's a kid that forgets something. I mean, hell, I once forgot a sleeping bag and I was 16. Oops.

Definitely be good w/ first aid, and be killer w/ a map and compass. GPS are nice, but batteries fail. Plus you don't want ot be the putz that needs to check the GPS every time there's a trail junction. Kind of makes it hard for the kids to get their orienteering badges if you're clueless.

Don't be a helicopter dad. On our backpacking trips (Weblos and higher), most of the time after we set up the tent, we were gone ... for hours ... until it was getting dark and dinner needed to be made. Just buddy system, make sure the kids pack their 10E's (we usually had a fanny pack or smaller backpack to keep them around) and enjoy your coffee as they scramble around and explore.