Agreed with others - It's been too much change too fast. Maybe you should consider getting involved with a GLBTQ friendly church, like the Unitarian Universalists. Having a relationship with God is very beneficial for teens, and I suspect Unitarians would also be poly-friendly.
I also agree with Green Mom - I'm not sure why it has to be a formal thing. Then again, I went on a date with a whole family, and the kids were great and didn't seem to be torn to bits by parents making a new friend - I liked the way the couple handles it... They have and make new friends, and seem to super slowly introduce new friends. Kids handle individuals and situations far better than labels. We should learn from that.
“Edit yourself, bitch. Edit yourself.” – Chad Michaels