Originally Posted by Anneintherain
and I ended up being politely semi-ignored by both of them out of respect for the other.
Hah, over-consideration combined with lacking communication can blow up in your face sometimes!
I would be somewhat passive towards my partner and try to initiate positive and non-threatening physical contact with the metamour, such as a good handshake instead of a wave when meeting, and maybe a hug when leaving? Depends entirely on the general touchy-feeliness of everyone involved, of course.
Although I do realize your situation has changed since writing this post, habitat, I'm still curious as to if this coffee date ever happened and as to how it went?