As Brian noted the sections of ETS on kids gives very good information. I have been a cub scout den leader for a few years and Doug's information is as good as I have seen on the subject.

Pay attention to how you dress them. Make sure they wear good shoes (old nasty but comfortable shoes are fine). Pack bright colored clothes. Do not put them in camo. I found some hunter orange caps on sale and bought some for my cub scouts. It sure helps keep track of them on hikes.