I agree that if you want to tell people now, tell people now. Don't wait because of a possibility of a false negative. From what I understand, that hardly ever happens. 2 test and some slight nausea if I get too hungry, sleepiness, and crazy vivid dreams are enough to convince me I'm really PG!
A lot of people do wait until around 12 weeks, because the books say that the time that anyone's risk of miscarriage is reduced drastically.
Personally, we, too, are waiting to tell mostly everyone, especially family. It's not that they won't be supportive, but since we weren't exactly planning this at this time, we want to get our ducks in a row, if you will. I totally relate to you a lot of you guys!