You know, I actually have an easier time imagining having an open relationship than I do thinking about polyamory. I mean, I get it intellectually, but when I try to think about what intimacy would look like, my brain balks. Perhaps it's just my own desires for an intimate "one" (and for me and many gay men, that's not necessarily sexually exclusive) ... but polyamory makes my head hurt when I try to imagine what the intimacy would look like. I mean I have more than one close friends and family now...but more than one "primary" intimate relationship?
To be clear: there is no judgement behind what I'm saying. Only wonder.
I found and read every book I could on polyamory when I first started having an interest in it. I even found an old, supposedly out of print book entitled (afair) "Group Marriage." One of the first ones I read was a "poly primer" that can still be found at many libraries, that included suggestions for documentation, legal forms, financial arrangements, etc. Unfortunately, there are only a handful of helpful books, devoid of judgment, available; I'm pretty sure I've read them all, even Heinlein's Stranger in a Strange Land, written way back in 1961 (wow, what a cool, eye-opening book for me to have found!).
For me, it took a reviewing of all I had ever been taught about what is "moral," what is "right," and what is "ethical," even. There can be morality, rightness, and ethics in many different living situations as long as the people decide what they want, are wanting it together and work towards it. The downside to poly that I could see was trying to balance your time and energy and have everyone feel included, loved, and special. That was the difficult part since life is how it is, and things don't always balance...just like with your kids. The sexuality of it seems to hang people up, but the emotional components are not much different than having 2 children you love, and trying to meet all of their needs, wants, but still having a unique relationship w/each of them, staying connected to them in a supportive position. Of course the adult relationships are not like parent/child, but I am only using that to illustrate that there can be jealousy, competitiveness, anger, scheming, etc., in a group of children with two parents, so it shouldn't surprise us when adults exhibit the same behaviors when the emotional or other needs are unaddressed/unmet. But I think the value of social support and validation to poly families cannot be underestimated, either. If the family does not feel alone, nor if they do not feel a need to "hide" their structure to anyone, but not have to explain it either, I believe that would go a long ways to helping them feel supported, understood and strengthened.