11-year old LL: Home run celebration?
 

Is there a rule stipulating players remain in dugout, even after deadball?

We had debate after entire team spilled out of the dugout to congratulate a player at homeplate for a homerun. 3rd inning and only one out.

Purely a sportsmanship question, not one related to negating the run.

Never heard of any rule that prohibits a team from going out to home plate to congratulate a batter after a homerun shot. If you watch the Little League World Series (with umpires that obviously know the rules), the kids come out to congratulate the batter pretty much every time after a homerun. Who took offense to the celebration?

It is just a part of the game and there is nothing wrong with it.
Quite often I hear coaches warning the congratulating players, "Don't touch him! Don't touch him!" as he rounds third, assuming that such contact would result in an out, but that is not the case.