Thanks for the questions. We realize we're in NRE. That's one reason decisions aren't actually being made. But knowing that they're decisions we're thinking of making is already a big step. We wouldn't even really consider it for another year, if we were talking seriously about it - various many circumstances keep us from moving any faster.
As for the two of them - they're not in denial about being bi, and they have sex, just fine. No toys (don't like 'em...) but the rest? sure. And they enjoy the hell out of it, ahem. They're not interested in any other women, never have been, and fit into a category of "mostly straight," which we found a couple of papers and articles about, as they were figuring it out.
As for being contradictory - yeah, as the weeks go by, we are interested in different things at different times. There was definitely a point when we all three wanted to be together as all three of us. Right now we're in a place where one-on-one dates are really treasured (and encouraged by the third person). Later, we'll change again. I would claim that's normal. I mean, it's true with my family, too - sometimes I want one on one time with members, sometimes I am all focused on the whole family doing stuff together. That's just human, I think.