We are going to tell our parents and siblings on Christmas morning. I'll be about 7 weeks by then, which is when we told them last time (Facebook not until after the 12 week scan!).
Yesterday, I bought a 6-12m t-shirt for our son yesterday. It's got the attached slogan on it. We'll wrap it and leave it til last on Christmas Day, then get our parents to 'help' our son open it.