I belong to the AA in my area, and we have a Young Alum Group headed up by one of my pledge sisters
She plans about 1 event a month, usually to a cute restaurant or bar in the area...or just dinner and a movie and uses Evite to send out invitations to everyone. I think we consider people under 30 as 'Young Alums' in general. There are over 120 people on the list...usually 10-20 at events, and it's not always the same people...so that's good. Even if people don't come to events, it's a great way for them to know that they can still hang out with DGs after graduation. Although I'm still in the area where I went to college and know some of the older alums in the area who were advisors to my chapter, it's great to meet girls from other places who have moved to St. Louis. In general, most of us 'younger' folk don't do the other Alum events (even though we're encouraged to)--but I know people get really bummed when they can't make a young alum event.
The 'leader' of our Young Alum Group is on the regular Alum Board and she is our liason to the older members (and their liason to us). The YAG is a great way for a lot of us (who probably wouldn't have gotten involved otherwise) to feel less inhibited by the Older alums. I suggest to try forming a YAG within your Alumnae Group. Get contact info. for those under 30 (email is a great way to send info.!) and try just meeting up and hanging out. The more informal the better!
Good luck!