You've been here before. Remember when you tried to get your students to read Pride and Prejudice and then watch the Olivier flick as a "treat"? Forget that Jane Austen and World War II are separated by two centuries. As far as your students are concerned, they're both in black and white and that's all that counts. You're going to come face to face with the "So what?" question.
Because we're dealing with the Holocaust, the level of apathy should be much less. But be forewarned: every day we're moving further and further away from the event itself. Most of your students (and maybe even you) will never have met someone who fought in World War II or survived the Holocaust, so the immediate relevance might be hard to grasp.