Brian,
Recent studies suggest that dynamic stretching is recommended over static stretching. Therefore your warming up should involve the ball as much as possible. Easy throwing, short passes, jogging, etc.. gradually becoming more demanding. Don't waste your time standing or sitting while stretching, especially with young boys who are probablly "warmed-up" before they get to practice.

I still stand by some simple streches then dynamic. the standard warm up lap is a must and it needs to be done as a team, it's not race! But don't waste to much time on warm ups get to skills and plays its more fun for all, including you! Have fun and feel free to write to me for any other football ?'s.

Brian there is a really good warm-up article and video at www.youthfitnessmag.com/warm-up