I told DS1(9 at the time)the day I found out. I was helping out at his school and told him at lunchtime. He was so excited, that before I had time to say 'keep it to yourself for now', he went tearing across the yard, screaming, 'Hey, X, my mams having a baby, Im gonna be a big brother!!!'
Cue the entire playground screeching to a halt and turning to look at me, wandering up 1 by 1 asking, 'miss, are you having a baby?'
Ad infinitum.