Until recently my being poly hasn't really been an issue as I didn't really have anyone to introduce the kids to any way.
Breathes has had outside love interests whom the kids have met as friends and they have accepted that explanation at face value.
We met when my guys were nine so they haven't always had the poly lifestyle in their lives. They've become LESS uptight about having friends over, and about meeting our friends, the more comfortable they got and the more mature they became.
Possibility is shy about showing affection in front of my kids but I think that's more so they won't go back to their dad with stories that could hurt me than being afraid to show affection.
I guess I'm trying to say that if you give them age appropriate information when they ask & give them the tools to deal with this information only good can come of it.