I so know how that feels. And it brings back good memories. You are very fortunate to be embarking on a triad when everyone is fond of everyone else.
Do you feel much compersion?
I don't think 'kissing and telling' applies at all. Once you embark on an open relationship, there really can be no more secrets at all. Everywhere there is a secret there will be a wrinkle, and where there is a wrinkle, there is room for bad feelings to fester.
Yet you said you have a D/s relationship....I still think the more honesty there is, the better, even in a D/s style (maybe even moreso).
in luce vive, vive in amore