First, congratulations! This is so exciting and it's tough to keep things like this to yourself, but... you really should for a few more weeks.
My doctor cautioned me with both of my children to wait until 12 weeks. The risk of miscarriage drops significantly after that point. My mother and MIL said the same. We told our immediate families (parents and siblings) around 6 weeks, but everyone else found out at 3 months.
The general rule of thumb is that you shouldn't tell anyone before 12 weeks that you are pregnant if you wouldn't want to have to call them should something unfortunate happen.
Wait a few weeks and throw a little party for your family and friends... just desserts or something easy and tell them all together!