Ask your WM what he thinks. Also, your state's Grand Lodge will likely have something to say about kilts in meetings, or at least the proper wear of the apron. For example, my state requires he apron worn UNDER a coat, yet some states require it worn OVER a coat. Not sure what the protocol for a sporran is; I wore my apron over mine.

When in doubt, ask the WM. It's HIS lodge...