Okay I read it and it sounds logical to me and I'm sure to others on this site, but we are xJW's. They are probably going to see the stance they are taking as "doing God's Will". They think they are suppose to shun you. From what you have told me your sisters are pretty cold-hearted. I don't think they will understand what you are saying, About putting families first, because they are taught to put God first, always.
Overall I think it's nicely done. You made a good point about the elders stepping down for their family, but the elder is still attending the meetings. Big difference from you, who doesn't go.
I wish I was more helpful. I just wanted you to be aware of what the reaction will most likely be.