I love what KC said about tailoring what/how you say things to the people you're speaking to. Making it as relate-able and understandable as possible is going to increase the chance of acceptance with as little upheaval as possible.
Hubby and I explained to our parents that we felt like we didn't experience much life before getting together (we began dating as teenagers), and that so many people who get married young like us end up splitting up. We don't want to feel like we're holding each other back or limiting one another so we prefer to be open. We both know we can love more than one person, so we specifically identify as polyamorous.
My parents think I'm living a life of adultery, but they are okay with it as long as I'm happy. Hubby's mom is more than happy to talk to him about Lady and seems genuinely happy that we are living our lives as we want to be.
With friends, coworkers, etc. it tends to just come up in conversation and we give a spiel about not believing in limiting relationships. No negative repercussions yet.