probably late with this but, i am totally out to my mom and dad about being poly. my mom and i have had talks about it and she has totally been at events where more than one of my lovers was there. but then, both my parents know i throw orgies and know i make porn, so my case might be different than yours. my dad is sorta confused about it, but he just rolls with the info i give him. i often wish my dad and mom were more interested in my life and asked questions about how things work, but that's just not their style.

i would expect for quite a while that they just may not get it, especially if they know you in a partnership already. they may feel as if you are doing something unfair to your partner or your partner is doing something unfair to you, if one or the other of you get another lover and are public with yer folks about it.

i believe in being real with my folks as much as i can. lots of people make other choices that work for them. i hope whatever you decide goes well for you.

I am out to my folks about it, and yes, it was interesting.

I started by telling my parents just that I didn't lead a monogamous lifestyle (I stopped by their house on the way to visit a lover other than the partner who they knew as my "boyfriend"), and waited for them to ask more questions. My mom asked a lot of them, eventually, and was really concerned for a while that I was being hurt-- she thought my partner was coercing me into adopting a lifestyle I didn't want, and that I didn't have the self-esteem to be able to ask him to be monogamous. She also became petrified that I was going to contract an STD--despite my practices being safer than most of the "monogamous" folks I know. Then once she understood that I was, in fact, choosing this way of loving and really didn't feel that monogamy was right for me, she felt that I was attacking *her* way of life and the way that she raised me for (this phase was shorter, luckily). I ended up giving her a copy of "The Ethical Slut"--the language in it is language that I know she's familiar with and matches up well with her own paradigms, and that helped a lot.
My dad, on the other hand, has never broached the subject with me. I don't know how he feels about it, and while sometimes that's hard for me--even the most rebellious of us wants our parents' approval and adoration-- I have to remember that it's his right not to be involved in a part of my life that he isn't ready to be involved in.
It's not something that my parents and I regularly talk about, and I'm not open with them as far as kink goes, but I do think that it's better to be out-- mostly because I want to be able to talk openly with my parents if something happens, or maybe make a date if I'm at home for a couple weeks without feeling like I'm sneaking around. Also, if my parents inadvertently happened upon some proof that my partner or I were seeing someone else, I've saved them the torture of worrying about having an intervention to let me know=)

The thing I would be most careful about is language--use language that's accessible to whatever their "norm" is. I know one of the biggest problems with my mom in my multiple "coming outs" has been my (or a partners') use of language that she finds to be unacceptable--dyke, slut, queer-- she reacted at first as if someone was insulting her baby girl, even if that someone was me=) I've eased her into the language that I use as smoothly as possible.

Funny stories? Two, and one of them not quite funny as a big surprise.
I was completely unprepared for the question, "Do you see others together or only seperately?" I thought the jump from non-monogamy to group sex was a large one, but my mother made it in about 2 minutes. I stuttered. A lot. So I advise that you know how you want to answer this question (or if you want to answer it).
My mother, conservatively dressed, in the suburbs, screwing up her face and saying "The Ethical WHAT??" That was totally worth the trauma on its own=)