A structure of helpers is a good approach.
Here is MY understanding of how it should all work:
The association manager co-ordinates and instructs the helpers what is required as regards summit definition. Prominence, how to find cols, data and format require by MT (a spreadsheet format), starting data (if any - e.g. SRTM) and suggested tools and map types to be used. This ensures consistency (mostly) in the provided data. Each volunteer (or pair of volunteers) is assigned a clearly defined region within the association to work on. Once completed the data for a region could/should be verified by one of the other regional teams and them passed to the association manager who perfroms a qauality assurance step himself before allocating the summit numbers (Ideally starting the lowest summit number within the region with the highest summits, giving them 10 points and down to the lowest with one point). The points assigned will conform to the points table in the ARM for heights of summits, which has been created to give an even spread of points across all summit heights in the association (i.e. not more high or not more low scoring summits but a balance across the heights and range of heights available - the MT can assist in chsoing the best points/height settings for an association) Once the association manager has all the regions (or all the regions that are to be added in this phase), he sends a combined spreadsheet (each tab a sepaate region) to the MT who once more verify the data before implementing it.
Often those who performed the mapping work to define the summits will be offered the role of region manager, to whom future changes (errors found, summits missed in the region, wrong summit name etc.) should be sent. In the case of a large association, it would make sense to have a second-in-charge to cover if the association manager is not available and to help in times of heavy workload.
That's how I understand the process to work.
As you can see, EVEN with groups helping, the critical work stays with the association manager and he has the hardest job of all. Echoing what Brian says, without an association manager who is willing and able to give a lot of his own personal time, you have no association.
Let me register my personal thanks to all association managers around the world for the great work they do - thanks guys (and possibly gals?).