Whats the hardest part of watching a school bus full of children go off a cliff? Your erection.
What do you mean to say with this comment?
It's funny, it has nothing to do with the missing kids.
Making jokes about children dying is highly inappropriate, as someone in your audience might have lost a child at some point.  Also, to imply that you take sexual pleasure in watching children die gives, what I hope is, a false impression of yourself.