One thing is the Mentoring program that can help Actives and Alums keep envolved.
I have contacted Actives over the years but never get any response.
One way for You to maybe get Alums re envolved is have a BBQ/Cook out and invite them over. Have an open house if you have one to go with it.
How about tailgating at foot ball games if You have a team.
If one looks at the donations by Alums, there needs to be a greater emphasis placed on Alums.
The start is at IHQ, and I still beleive The High Rho should have a stronger emphasis at the Zeta level to keep Alums updated and informed to keep interest.