You might want to include some information of relevance to your campus. For example, at my university, the Greek Affairs Office always published/made available the average GPA of each fraternity and sorority as well as the all-campus men and women's average GPAs. If you have some especially sharp greek students, this might work well. Also, do a quick poll of campus student government leaders to find out who is greek and who isn't (usually the greeks already know this).
Since I am a university administrator, I am a member of the National Association for Student Personnel Administrators (NASPA). Among other things, I belong to NASPA's Fraternity and Sorority Knowledge Community. Our special section of the website includes a list of references and research abstracts. I have included this link to the knowledge community below. Though our committee is not anti-greek by any means, please be advised in advance that the research currently cited/reviewed regarding alcohol use reflects negatively on greeks. I wouldn't argue the "we don't drink more than non-greeks" point unless you've got some good studies to back that up.
http://www.naspa.org/communities/kc/...ity.cfm?kcid=6
.....Kelly