Randy,
It sounds like you have a pretty clear picture of the challenges you face.
As you think about an alumni website for your school, consider what would draw your graduates. What things could you include that would provide that "buy-in"?
You might consider components that alumni are looking for like a Job Board, an Alumni Directory (to connect with old classmates), or other helpful information they might be interested in - Career Services, Loan Info, Continuing Education. You may also want to consider some things that would, literally, force them to your site like Transcript Request Forms or Grad Surveys.
Creating and maintaining a website definitely takes a level of commitment, both financially and in the area of personnel needed to manage it. That being said, it is a fantastic method for communication. Often schools spend an incredible amount of money trying to find and maintain contact with their graduates. A website that includes Alumni Profiles where grads can update their personal and employment info accomplishes that same thing. In fact, graduates will find YOU via a website rather than you attempting to find them.
June