First of all, Congratulations!!! :)
I think that was a really cool way of telling everyone.
Maybe they didn't respond because it just hasn't sunk in yet. With the holidays and everything going on maybe they are just kind of on overload. Hopefully by next time you see or talk to them they will have had time to think about it and they will be more supportive. I think I would just let it go at this point and wait and see if they come around.
When I told my family I was pregnant with my second, they all seemed really happy except my Dad. It ended up that he was just worried about my daughter and worried that she wouldn't get enough attention or that she would be jealous. By the time my son was born, he had come around though. Some people just need time to adjust to new ideas - hopefully that's the case with your inlaws.
Try not to let them bring you down. I would have been disappointed by their reaction too. It might be best to just wait it out and give them time, but if you have to be around them a lot and they still seem hestiant about everything, I think I would say something like "I'm worried that you guys aren't really supportive of the idea of another baby." Hopefully you won't need to though and they will be bettet the next time you see them.