Runic Wolf and I don't tell our 10 year old that we're poly, though Runic Wolf did call his ex his girlfriend infront of him and it seemed to completely go over his head. Wendigo is here a lot, as are a handful of other friends and I am a very cuddly person, so don't avoid showing affection infront of him, though I've never kissed Wendigo infront of him. Runic Wolf would hug Loveleigh and kiss her forehead infront of our kids (she has 3 that live with her and we have 1).
Wendigo's son knows that we're friends, but he's 16 so we're more careful about keeping our relationship from prying eyes. Though we've been known to make out in his driveway when I take him home at night, we're careful to make sure that the car lights are off and that it isn't obvious that people are awake in his house. I remember last summer they had a dumpster in the yard and we'd park on one side of it, we started making out and then heard splashing coming from their pool on the other side of the dumpster. His son and nephews were still up and swimming after midnight. They couldn't see us, but it definitely reminded us to be more aware.