K.D.
Everyone has given you great advice. I was so happy for my sister-in-law when she told me she was pregnant even though we'd been trying for nearly a year. It wasn't her fault I wasn't pregnant so I would never be bitter towards her for being able to get pregnant. And then when I finally did get pregnant, I had to call my other sister-in-law and tell her knowing that they, too, had been trying for years to get pregnant. I just told her that we were expecting, gave her the due date and she asked a few questions and that was it. She never made me feed weird and was genuinely happy for us. (They later adopted two girls.)
Anyway, my point is, like all the other advice, share your news and then drop it. Don't be surprised if they don't ask much about the baby and try to refrain from talking about it too much when you're with them. It doesn't mean they aren't happy for you, it might just be a little too much for them to handle right now. But don't hold your news back, they'd hate to find out from someone else.
Congrats and best wishes for a happy, healthy pregnancy.