AKA_Monet,
Since you gave me a good response earlier I'll try and do the same.
My org's alumnae chapters can range in size from as little as five to as many as 60+ members. Obviously the smaller chapters will not be able to organize something on their own and their support of philanthropies will mostly be monetary. The larger chapters would have the manpower to create a community event and probably help the collegiate chapter with their events as well. It's very different for every alumnae chapter.
Also, there are only 4 NPHC sororities which I assume are fairly well distributed across the US. You can go to most any state and find members from each org. For the NPC groups, though, there are 26 of them and except for the hugest ones they are strong in different regions of the US. A group might be huge in the South and barely visible in the Northwest, or vice versa. So sometimes just getting 5 women together is a battle. I think NPC should be doing more to solve this, but that is a topic for another day.
Hope that cleared things up a little.