I went round my family 1 by 1 and showed them the 8 week scan picture it was funny handing it them and them looking at me confused like hmmmm what's this? lol she was just a blob back then....
Plan a gathering. Seat family members immediately upon arrival. Just prior to the Appointed Time, get the 5 yr old real hyped up on soda, filled with details of a sibling-is-on-the-way, and how excited everybody will be to find out.
Have 5 yr old enter room last, via helpful friend.
Have the camcorder rolling & capture the scene!!!