19 and TTC

I'm 19 and want to start a family. My boyfriend and I are independent. We have our own place, pay our bills (needed help one month, but other than that it's all us), he is an electrician making pretty good money, I don't plan on going to college (which is another reason they'll be disappointed in me and a whole other story), and we are TTC our first month. He has already told his family that we want to, and his mother is very supportive. What I'm afraid of is my family. I feel my mom will be oky because she had her first at 19 too (although not planned). My grandparents are the ones I'm afraid of most. I KNOW they're going to be very upset and disappointed.  

 Sorry for the long story to this question, but how (when it does happen) will I tell them that I'm pregnant?