Awesome. Welcome to the club, coffee and doughnuts on Thursdays, Fridays are karaoke, and t-shirts are available out in the lobby.
Seriously though, its great that you're taking a step you feel will be meaningful to you.
I do have to be Captain Buzzkill and ask a couple of questions, feel free to tell me to fuck off or answer them as you see fit. If nothing else, they are important to ask yourself.
First, have you run this by your manfriend yet? I know you are "both passionately looking to explore the loving and sacred ways of Polyamory" but I mean have you actually sat him down and had a big long conversation, making it clear as fresh glass that this is the way you want to live, that its not some phase or fad, that you still love him and want to be with him? If you have talked to him, is he on the same wavelength as you?
Second, have you thought about and developed some plans for dealing with the world? A poly relationship IS still technically illegal in some states and there are a number of professions that dont look kindly on it. How will your family react? Are you prepared to find out that certain friends had parts of them you never knew they had?
Dont get me wrong, I'm not trying to discourage or dissuade you in any way. Polyamory is one of the best things I've ever embarked on in my life and I say that with absolutely no reservations. There are no small number of people who would echo that statement around here and I'm always happy to see our numbers grow.
But these are the kinds of things I REALLY wish someone had smacked me upside the head when I first started identifying as poly and asked me. If I had sat down and thought of them, I'd have avoided a seriously messy introduction.
I wish you and yours the very best, whatever happens.