All of my kids live with me.
To be honest, the honest and openness of our life in general, combined with our honesty and openness about what changed and why has been AMAZING.
None of them have had an issue, nor did my little sister (17).
Also-all of their friends are ALWAYS hanging out here, and none of them did either.
I really think that kids handle well what adults handle well.
The issue (imho) Dinged in your situation isn't "polyamory" for the kiddos. It's shitty handling of adult behavior (not pointing fingers at you, just the things you describe, like bailing on a family activity-way uncool behavior for an adult)..
Anyway-I have LOTS to say, but gotta go back to the hospital to drop off some stuff for Spicy Pea.
On a side note-Everyone is doing MUCH better today.