Hi Coco. Welcome and I hope you find the answers you're looking for. For me I had a lil help with this when I had to tell my friends that I preferred big women. A bunch of people thought it was a phase and I'd find a nice thin woman to make me happy. BAH!! I had to deal with explaining to people why I preferred big girls.
After that experience, I was able to pretty much just tell people this is how I lived my life. I wasn't looking for support or approval, it was just how we lived our lives. At first people were very hesitant and skeptical, but then I introduced them to our significant others and they realized that everyone was...NORMAL!!! That's right, us Poly folk aren't all nutjobs!! Ok, I'm slightly nutty, but that has nothing to do with being Poly.
Anyway, live your life for you and don't worry about what other people have to say. If they can't accept and be happy for you, then maybe they shouldn't be in the picture. I told a few of my friends that and every single one of them is still around.