I think in that situation I would get down on the floor with them and help them pick up the berries, ie. see if I could cajole them into doing it with me like it was a game. Or, if they simply refused to do it, I woild physically hold them while I gave them a time out (though how you do that with two kids I don't know; I've only ever done it with one). I wouldn't let them play or goof off in other words, I would hold and restrain them from having any fun until they calmed down and were willing to be compliant. I would avoid hitting (not that I haven't done it), because I don't think it works and it just builds resentment.