My daughter,five years old, asked me yesterday how she arrived in her mother's belly. She knows how she was born. She knows that before that, she was inside her father. So, now she wants to know the conection from her father to her mother. She knows about our genitals, we bathe all together and she has seen me urinate. Now, how can I explain the sex act with an appropriate answer for her age?
At this curious age you can answer her in a direct manner. At this age she will comprehend and absorb only as much information as she can handle. I am somewhat worried about your words "... before that, she was inside her father." I understand what you are attempting with this explanation but she (the baby) wasn't inside you at any time. Your sperm had to enter her mother and join with an egg from her mother's uterus before she was conceived. I think you can tell her something like: You were made when a sperm from daddy's penis got together with an egg from a part inside mommy called her uterus. Daddies put their penises inside mommies' vaginas and then let the sperm come out of their penises to go join up with the mommies' eggs. We call this making love or having sex.
I know you will always include the importance of love and your family's values as you give your kids a healthy sex education.