Good luck with it!!
Like Pish said, just say it proudly and strong and how happy you are. Even if they aren't excited straight away it will grow on them =)
My mum always tells me the story about when she told her mum she was pg with me, it was a month or so after their wedding and all grandma did was nod and go 'thats nice dear'. the next day after they left they got a phone call from grandma over the moon and crying she was so happy for my parents. It was only because she had had a chance to look at the calander and saw that yes, i was concieved after the wedding that she was ok with it =)
but if you and your husband are happy and it is what you want then thats all that really matters.
good luck!! and congrats!!!!