Yes, I think kids need to hear the story of another person who got in young, and be given a few key warning signs, such as:
Beware of any group that:
- tells you they have all the answers
- discourages you from listening to people outside the group
- tries to occupy all of your time
- tries to get you not to trust your family and friends
Age-appropriate materials could be developed, of course, with the older kids being shown programs such as the Four Corners one or "How to Spot a Cult" (what a great title).