A formal would be fun! I wonder if you could entice a bunch of recent sorority alumnae to coordinate that as a Panhellenic thing-- it could be for alumnae of any sorority to attend. Proceeds could go to benefit the local alumnae panhellenic, which would then be put toward scholarships for collegians
I'm sure that would be a great topic for your town's next Alumnae Panhellenic meeting! And you could advertise it locally, in alum newsletters, web sites, emailing, local churches, Junior Leagues, etc....