I don’t know anything about this program specifically, but speaking about these programs in general: I’d be concerned that a child might (1) get age-inappropriate details on what a molester plans to do to them, or (2) get the idea that abductors and molesters are lurking behind every bush or tree.
Is it possible for you to attend the assembly, maybe sit or stand in the back of the room? That way you can discuss the content with your child afterward. The latter impression (2) you could correct after the assembly, but too much information (1) may not be eraseable.
What if you declined to have your child attend the assembly, but you just went through the materials privately with your child at home. That way you can teach your child the necessary information without being too scary.