With the current threats of nuclear war hovering in the air, you might want to consider exploring John Hersey's book Hiroshima with your students this fall.
Hersey interviewed survivors right after the atomic bomb was dropped on Hiroshima, and this book is his account of the event from the point of view of each of six survivors.
An historic account of the event, this book will give your students the real picture of what nuclear war looks like from the ground level. Have your students additionally explore how the bomb was developed, the mission of the Enola Gay, the reasons why the bomb was used, and the surrounding moral/ethical questions.
Use all of this information as a springboard to discuss the threats present today. Compare and contrast them to the circumstances when the bomb was dropped on Hiroshima. Discuss students thoughts and anxieties about the new nuclear age and ways to cope with a nuclear world. Guest speakers (counselors, foreign policy experts, etc.) would be good to incorporate in a unit of study.
It would be good to keep the nuclear threat in historical perspective. We've been living with the threat of nuclear war since the bomb was developed in the 1940's, and to date, the only bombs used have been on Hiroshima and Nagasaki. When I was in elementary school, we did the "get under your desk" drills; it's something everyone in the modern world has to find a way to live with. The best thing you can do for your students is to make sure they know the real facts, not just media hype and unsupported stories and opinions.