I remember you posting about this before; your poor friend. What a tragic situation to be in. 
I think on the card front, I'd have 2 ready. One as you mention, a blank card for your own message - the starry night scene sounds lovely, for if he dies at birth or survives only a short time. I'd have a second card though, a normal congratulations on the birth of your baby card, in case he does survive beyond what the prognosis suggests. With the starry night card ready for if and when he does pass away.
Such a sad situation. I'll be thinking of them (and you) today; and will pray for them and their baby.
Noah Gabriel 11.06.05 
Elijah Cameron 28.04.06
Sebastian James 15.05.08
Nathaniel Joseph 04.06.10