I am part of a V, myself, Maca and Greengecko (GG). We have Sourpea (bio child of myself and GG), Sweetpea (bio of Maca and I), Spicypea (mine from previous circumstances) and SaltyPea (bio of Maca and exwife).
Ages-Spicy 21, Salty 16, Sweet 12, Sour 5. (salty doesn't live with us or have contact by his choice not related to poly)
We are out with the kids and have been for 3 years.
Honestly, they took it easily and well and it just wasn't a big deal.
I bet that a short honest discussion about love would resolve the anxst you have over your 11 year old. Kids really aren't too particular about who loves who and they ask what they need to know.
We didn't discuss sex per se-they didn't ask.
"Love As Thou Wilt"