What a dumb move. All they had to do was discretely give notice to the parents ahead of time and they could have easily separated the "scare kids" from the "no-scare kids." They could have gotten away with scaring the shit out of these kids and not have to deal with these complaining parents. Hell, I bet some of the parents would have even paid the staff to have them film their kids being scared. I know I would. Cherished Memories...
And in regard to the obligatory bash America post, Do you honestly believe only American parents would react negatively to their kids being led to believe they were going to be killed?