When coaching my 6-8 year olds, I realized that many of them would be in place to make a flag grab, but the flag would seem to slip right through their hands. I attributed this to their lack of hand-eye coordination, due to their young age. Concentrate on drills at practice that not only teach them to swarm, but give them the repetitions of actually grabbing the flag. Put them all in a 10 by 10 square and make one of the them the only flag puller, while everyone else runs around juking/spinning etc. Make it a competition by seeing how many flags each person can pull in 60 seconds. There are other some other specific exercises that can be done to specifically hand-eye coordination without the flags. Not that I required the whole team to do this, but I had my son practice grabbing racquetballs in several different fashions, and I swear that his flag grabbing improved immensely. And of course, you could always put your kids in a fenced in yard and have them chase chickens (cue the Rocky Theme) hehe.