Question regarding creating a project involving groups

I would like to create a project that involves having a group take on a task - in this case having everybody maintain a certain diet for six weeks - and then having each member of the group be able to chart their adherence to the protocol regularly; ie they have a place in their blogs where they can tick off how well they did that day and a place where they can tick off how well they're feeling...

Any ideas what plugins I should use? I was thinking of Custom Press?