Our BF was an acquaintance that we're both very fond of, and keen to be closer with. Our GF is a long-time friend that, when we came out to her, revealed that she has been in an open relationship with her BF for a few months, and has had a crush on both of us for a very long time.
So yeah, we're pretty lucky. GF lives far away, but is staying for the entire weekend, and we're very excited. Planning once-a-month visits from her, and probably more often from the BF, as he's not local, but is much closer.
We're prepared for things to be occasionally difficult and problematic - what relationships aren't? - but are enjoying being on this journey together. My wife is possibly the most awesome person ever, and we're in an incredibly strong place in our relationship right now. So all seems well for the time being.