Hrrmm....toughy. My (local) sorority didn't have a mothers pin or ceremony to go with it. But I think having a mother's tea/brunch/day thing would be nice, and incorporate a pinning ceremony into that as well, so it isn't just the ceremony. Maybe incorporate some of the alumnae into the mix as well, to reinforce the idea of sisterhood extending outside of college, and reinforces the sorority as a supportive place for successful women.
*EDIT* never mind, someone beat me to it!
