Depends. If we're working a game in the league where I'm the AUIC, then I have the authority to order everyone off the field, and I do. Other games...well, they mostly listen to me. I haven't had a situation where a very even "Coach, you are jeopardizing the safety of your players" audible to the gallery didn't do the trick.
The rule in the league I am the AUIC for goes as follows: see lightning, hear thunder - and I'll usually take parents at good faith on this one, because they don't want kids getting hurt...well, most of them - play's suspended for thirty minutes. If in that thirty minute period another sighting occurs, the game is off and the field is cleared. If no sighting, back out and resume play. I'd give the pitcher eight down the pipe, at a fast pace.
I like our rule. We haven't had any trouble with kids getting hurt, just with my kids (the umps) not enforcing it. I've had to chew several out after getting talked into continuing by coaches. Of course, I had the Board of Directors suspend the coaches for knowingly violating the rules...ain't I a stinker.
