The Philadelphia Alumnae Panhellenic is very much like this. We have 21 of the 26 NPC sororities represented, some with more than one alumnae group. We do not involve the greek advisors from area colleges though. Each year we have our big scholarship and awards luncheon, where we give two scholarships to two deserving collegiate women in the Philadelphia area. We also have a silent auction and a drawing for gourmet baskets. Each organization makes a basket up of at least $75 in value and those are used in the silent auction. It's a really nice event, held at a local country club.
I wish our Panhellenic was more responsive and involved with actual collegiates, but at this time, that doesn't seem to be the case. We do philanthropy and donations to a local women's shelter, as well as donating money to causes.
I will add that I had nothing to do with the starting of the org though. I just became our rep this year.
Good luck
