Can't help adding my own two pennies having read the thread all the way through. Despite being a mono hetrosexual with traditional views who finds the idea of a poly relationship miles from what I would ever want, I have been impressed with the way the OP has replied and it has really made me challenge my original view. It has made me realise that just as I feel so passionately about being in a mono relationship with my husband, other people will feel as passionately about being in a poly one, and therefore what is so wrong in that. I get the impression that OP and her DP and his OSO show a great deal of respect, love and care for each other, and that is something that is so vital in a relationship regardless of what we wish to label it.
I don't think OP is being dishonest in any way to her children, she is showing them consideration and love by wanting to make sure she handles the disclosure of her relationship situation in the best possible way. My DH and I haven't told our children everything, they don't know he was previously married for example. I don't feel it is dishonest, we just don't want to burden them with elements of our personal life until we feel it right.
Someone mentioned OP could try some Muslim sites for info about poly relationships, but I think given she said that this has nothing to do with religion I'm not sure that would be relevant personally.
OP - when I was expecting my number 2 I joined a "Due in ..." group which quickly moved onto its own Facebook group. After my 12 week scan when I discovered number 2 was also number 3 I got invited to a twin group in Facebook and I am still a member and find it a really supportive group. It is a closed group and people have to prove that they either have twins or are expecting twins to get accepted into the group. It started out as a more relaxed entry but we had a troll and so moved over to stricter entry criteria. You could not meet a more supportive and friendly bunch of ladies. Perhaps you could set up a similar group in Facebook, and people who have posted here in mn who seem genuine could join. They may know other people in poly relationships who might like to join and they know others etc and before you know it you could have a large online community, safe from trolls, of people who support and share experiences with each other.
I must say I don't find the original post attention seeking, just someone trying to reach out and find those people in a similar boat, like I have done with my online twin mummies group, with whom you can chat, ask advice, rant about your life without being judged or people simply not getting it (I would certainly not have a clue about the challenges of being a twin mum if I wasn't one, so I find other twin mums get what I'm going through more than other people).
The criticism over some of the language or acronyms is quite laughable given how much I have encountered since following a few posts on mn, it is littered with them, most people don't realise they're using them, so OP ought to be cut a bit of slack for that. I can't remember who posted about it being only mono hetro people who go on about sex all the time, but I thought it was a brilliant post! OP didn't kick off with the sex info, she got asked lots of questions, and I've seen the grief people get if they don't respond to these questions, yet seems you get grief if you do too! I hope you find a forum with supportive people who are in the same boat who can share their experiences and advice with you OP. Thank you also for this post on mn which has certainly challenged my thinking and made me more understanding and tolerant of others.