Yes, every relationship is different. I am the hinge in a polyfil V with two straight men, and have been for almost two years. They are not best friends but they are family and we communicate a lot even if we live in different countries. I will not disclose anything sexual between them but otherwise we are a family that shares most things. My guys talk to each other a lot, even if we most of the time live in different countries. Right now we are living all three together in Turkey for the summer. Our big, big rule is the every other night rule - I share their bed every other night, no exeption come rain come shine. They both get involved if I have an issue with one of them (texting me stuff like: I suppose he didn't mean it. Try to forgive him) and I am usually voted out, as they agree with each other 99 percent of the time

we don't know yet where we will permanently live, but I have learned Turkish for 1 year and husband is starting to, and boyfriend is learning Norwegian. We have briefly discussed kids and there is an understanding that there will be kids at some point (when our economy is better, anyway). They are the loves of my life and I would do nothing to hurt them. That is part of the reason we have kept the relationship party secret so far, to give us the uppertunity to get close as a family before presenting us to the general world. But the official site of it in our country has been good so far - my boyfriend is even getting visitor visas as my boyfriend, despite that I write on the forms that I am also married - the didn't care about that at all, just wanted to know if I had met his parents! (I had) It is also perfectly legal to live together and there is a famous V with kids in my country that lives with kids and no problems.
To talk to kids about poly, I think the simpler the better. She is our girlfriend will go far. Or talk to them about what it will practically mean in their lives, or just let them get to know her gradually.
To explain it to your family in romantic terms, I have yet to do that myself, but the way I tell my friends is that is like regular love exept there are two relationships and three people to support each other. I am thinking about writing my family a letter, to be sure that I get to say all I want to say about it, or at least write down some keywords for myself. As of now, I am easing my social circle including my family into knowing that I travel a lot, learn language, have a "close friend" that I see and so on - it might make more sense to them when they connect the dots that I am in a regular international romantic elationship, exept my husband also sometimes travels and learns language, and that all three of us prepare very seriously for the future.