DS is almost 3. I am 10 weeks so we haven't told him about the pregnancy yet - we have talked generally about Katy on Cbeebies and I have picked up a few "new baby" story books which he is interested in.
My feeling is to wait as late as possible to say anything, as otherwise 6 months is a long time for a little person to wait - but how do you deal with other people talking about it? A friend of mine already tried telling her DC about the baby in front of him when I was only about 7 weeks!