You don't need a rule for this. What you need is a coach with some class who will put in some reserve players after they get a big lead. You can always put him back in if they start to get close. The kids will never know what you are up to, and probably half the parents won't either. You win the game, the all star gets his touches and some stats, the reserves get some playing time, and ALL the kids keep a little dignity.
+1