I can say from attending the vigil in Indiana, there were quite a few of BMs family members present (as was AM, of course). It seemed that everyone there was respectful, MOO. Hard to know if it would have been significantly different if BM himself was there, but I agree that 99% of people would see the daughters for the victims they are and be supportive.
It will be interesting to see what BM does with the vigil. On one hand, it is bad form to skip your missing wife's vigil. On the other, we have yet to see BM put himself in a situation that isn't fully controlled. My money is on a no show (I'm going with a "feeling ill" excuse - maybe he ingested some expired peanut butter). JMO.