How to tell my family?

I'm 18 and I'm pregnant now 12 weeks. I've told my parents and my SO and some close friends but I'm scared to tell my family mainly because of my age plus no one knows the guy. My first doctors appointment is Wednesday and I'm thinking about telling them some time after that but I'm not sure how to tell them to where they'd be more accepting of it. Like who to tell first? Should I act excited? I mostly am unless I'm around my parents who are upset about it.