Thanks for all your input. It's interesting to hear how others go about this kind of thing.
As I said, it's okay with me however each of them wants to proceed -- although the running in the same circles thing concerns me.
Ideally, for me, I would want us to be able to all be together at the same time, and though they wouldn't have to like each other, I'd want them to be courteous and civil.
BlackUnicorn -- actually I would say they're romantic involvements. It's not the way I think about it exactly, but it's a distinction that would matter to each of the two of them. I guess you're right that in the early stages the scheduling might work best.
Derrythe, I do think they could click, but I'm not sure they could get past the idea of "sharing" at the same time. Although, having said that, they probably don't know yet if they'd handle it either! It's not like I go out especially looking for polys to get involved with, and with the majority of people being monogamously inclined, it tends to happen that I get involved with people for whom this whole idea is very new. It's like we're all just figuring things out as we go along. It's fun and refreshing to not have to impose arbitrary limitations, but with no rulebook it all just gets a little confusing :/
Redpepper, that is what I would most prefer - having a sit down and chat all together. The division of time thing is always an issue -- there are only so many days in the week! I also completely agree with what you say about respect and civility etc, and I would trust them to be that way towards each other. I just worry about awkwardness etc.