Hi S.! First, congratulations on your great news! I had a similar situation arise recently, as I am currently 7 weeks pregnant with our second child. The weekend that I found out I was pregnant, my husband's entire family was in town. I took the test the morning of a big bbq at our house. There was no way we could contain our excitement, so we told everyone! It made for a great day.
Let me further back this up by telling you that I also suffered a miscarriage last September. Like you, we have believed in sharing our baby joy right away. (We did the same with our first baby too). All of our family knew that I was pregnant and I have to tell you that when I suffered my miscarriage, it helped sooooo much to have that family support. If our families hadn't known, then it would just have been my husband and I going through the miscarriage alone. That would have been much more difficult. There's nothing like having your family rallying around you during times of turmoil, and I definitely think miscarriage is one of those times.
So I say shout it from the roof tops to your family if you want to! Families are there to share our joy - and our pain - so if the worst were to happen, won't it be nice to know they're there for you?
Good luck! And congrats again!!