Yes, i told them that they’re going to have a little brother/sister to play with soon, and that the baby is in mummy’s tummy. For my third pregnancy, my youngest daughter was obsessed with my tummy. She used to talk and sing to the baby 
Of course, and i already have, given that both my girls attend school.
I disagree. We’ll be explaining the birds and the bees, growing up, puberty etc, to them when they are “coming of age”… just like my parents did to us.
Sure. It has to be done. I’d rather them get their source of information from us, their parents…rathe than nonsensical hearsay from their friends.