No, it's not too much for first grade.
Remember, they don't understand the entire story as we do. All they know are the very simple facts and they relate them to what you've taught them about animals and people. So, if you haven't taught or let them learn kinky things,
then you're good to go.
My daughter told me in kindergarten that mammels were "little hairy animals that came from their mommy's tummies where it was warm and drank milk." I'll never forget that. Made perfect sense to her.
