I'm going to tell my future sil's they are no longer bridesmaids at our wedding
Why will you be doing that?
They have been against the wedding since day one and I don't know if they will cause a lot of trouble or not there.
If your bridesmaids have differences against who you are marrying then it is not that easy to determine what to do. But in this case you should not hesitate to eliminate them. People will wonder and be embarrassed but all in all it is not worth the possible destruction they could cause being there.
The wedding is the most important day of my life so they need to drop their stupid ideas and support us as a couple.
It would make sense to leave them out. If they are trying to stop your marriage, they don't need to be a part of your wedding.