I've been told that it's normal behaviour at 4.5 to be interested in willies etc, and this will probably be intensified by the fact that I'll be giving birth to baby number 2 in about a week. DS doesn't know anything about sex other than there is a baby in mummy's tummy which grew from an egg, and it will come out of her tummy like he did (c section) but some babies come out of their mummy's vaginas.
How can I walk a comfortable line between 'willies are perfectly natural' and 'willies should be kept private'? Any good books out there?