Perhaps this has been suggested and dismissed for whatever reason already, but has anyone looked at creating a form for co-op sign ups? DH was using one tonight and I'd never seen it before.
Go to the "Create New" drop down menu on the left side of your Google Docs Home and select "Form." You can make it like a sign up sheet so other people can just fill that out, and it'll all go into a spreadsheet on your end. Keeps personal info private and easy to distribute. Might have capability of "turning off" after it reaches a max number of entries, too. Just a thought!