First off - CONGRATS on your pregnancy
Since you're over 35 they will do a bit more genetic testing, as your risk raises with your age.
There is no specific "safe" time to tell people, it's when you feel it's right. Many women wait until after the 1st trimester (12 weeks) to tell people as that is when the risk for a M/C goes down considerably. Other people tell right away.
I think we broke the news around 9-10 weeks just because we were so excited!
I imagine you're due in August - if so check out the August DDC on here, you'll meet a bunch of girls who are due at the same time as you.