I am digressing a bit here, but I strongly encourage you to rethink this.
The act of hearing things they are not sufficiently mature to hear is the very best process for becoming mature in that way.
Of course I am not speaking of prurient matters or horrific tragedies (you should hand them neither Penthouse nor MAUS) but I think you should explain matters like the one at hand clearly, in an adult manner, and with adult vocabulary.
They may not understand more than 10% of it but that lack of understanding is a great challenge and the 10% they do grasp is a foundation for deeper thought.
I have three children and not only do we speak of things that are beyond their ken, with them, but we make a point not to adjust our vocabulary downward when we speak with them. They have risen to the challenge.