hey jac - from the sound of it, I think only one of your girls will be able to make it. at least, that's the way I'm reading the responses from my group. I'm assuming those with potential money issues are just delaying the inevitable, and that's ok. some people just don't feel comfortable saying no, so I'd rather think they're not coming and then be pleasantly surprised if they do. this happened with my MOH - she was part of our moving the wedding a year out because the got pregnant and would have been due right around the wedding time. a few months later after we sent the STDs, she called me freaked out about costs (which we had discussed at length previously and she swore weren't an issue). hormones aside (she was 7 - 8 mo pregnant at this time), I figured she was pretty set on not going - she and her husband even committed to join his family in hawaii when the baby was six months old - after knowing about my wedding previously.
my point is, if she was really intent on coming, I think she'd be considering going alone (so that both of them wouldn't have the expense and the need for someone to care for the baby) and talking to one of our mutual friends about sharing a room, etc. I'm not trying to be critical of her priorities - it just became clear she couldn't do everything, and the wedding was too much of a sacrifice, which is really ok. but I'm not looking to her for a definitive 'no,' I feel like she's already said that in a number of ways (citing financial issues that weren't a problem in the past, going on the family vacation and not planning to go to the wedding alone - whatever it takes).
and as for the symmetry, I think my FI and I will each just have one special person with us - we may not even have them stand during the ceremony or wear anything particular. not only is it infinitely simpler, it requires fewer choices (hopefully there will be at least one friend there, right?? ; ) maybe it's as simple as saying, 'hey, we're placing an order for clothing and need to know if we should get something for you. please send your measurements if you'll be there.' but I wouldn't do the ordering unless you were REALLY confident they were coming (I'm assuming you're paying for everything here). if they decide to come, I think the wardrobe would take care of itself in some fantastic, pre-destined sort of a way. but I think you already have your 'no's.' order for those who are yes's. : )
best of luck.