M.M.
You say 'CONGRATULATIONS' you buy a card and a gift. You take a meal and you say you cannot wait to meet him!
My colleague's son was born with a severe disability and every one else except one guy and i chipped in and bought a gift and treated him like another other parent who had just had a child. He cried when we gave him the gift and years later when I ran into him on a vacation he said 'thank-you' for treating us like parents with a newborn child and not ignoring his son's birth and avoiding him at work like everyone else.
I'd say ' you can look forward to a million hugs , laughs and kisses' because if you have ever spent time with a kiddo with a bonus chromosone then that's what you get.