Kurt is a good, safe mountain guide. Those kids were in far less danger than during the drive to Lone Pine.
Notice two safety precautions taken:
1) All the members of the party are very close together in the chute, thereby lessening the chance of being hit by a loose rock moving a terminal velocity. Good practice for any climber.
2) Kurt roped them up for the final push, even though the last 400 feet are "only" Class 3. Another good practice for people new to the game or uncomfortable with the exposure.