When should I announce my pregnancy?

I'm 5 weeks along. I work at lowe's and I'm on my feet all day constantly running all over the store, so by the end of my shift I'm exhausted. This is my 3rd pregnancy, I've had 2 prior missed miscarriages. I have my first prenatal appointment next Wednesday the 9th, I'll be 6 1/2 weeks. Here's the thing I'm going to Maryland to see my cousins on July 12th, I really want to tell them especially since I'm going to be in a bathing suit and my belly is already sticking out. But what are they going to do at my first appointment? How do I know everything is alright?