One thing I have come across from various religious folks who don't understand atheism is, "How do you talk to your kids about death?"
It's actually not that difficult.
I had this conversation with Puppy the other day.
P: Mommy, when people get too old, they die?
(His great-grandmother died last year; the only "real" death he is aware of)
Me: Yes, that's true. No one lives forever.
P: That means YOU could get old and die? (His voice was starting to waiver a little).
M: Yes, it does. Everyone dies sometime, but I won't be old for a long, long time.
P: Even ME? I could get old and die? (Tears definitely near the surface now).
M: You won't be old for a long, long time. We can't live forever, and really, no one would want to. But you don't need to worry about it right now. We just do our best job to stay safe and healthy so we can get old. That's all you need to worry about right now.
P: Oh. Ok. Can I play with playdoh?
Yep. That was it. No need for fairy tales, no need to lie, and no need to burden a 3 year old with the other reasons people die before they get old. He asked his questions, got the facts, and hearing the truth was all he needed. Life goes on. Hopefully for a long, long time.