For me, like most, it all depends on how much as well.
I suppose what would be best is to run some scenario's past you.
Lets say 50 members want to be involved and lets say we produce a 120 page (60 sheets) book with hard cover (2 pages per member + 20 pages of fluff and text). I am not sure on sizing, but I would suggest a minimum of 8x10inch pages or even A4.
Now, using the 50 member base, I would think that anything more then a 100 book run would be a waste. So, how much would that cost in round about figures per unit (based on what you have said and the services that you would offer)? How would this change if there was 200 books produced? How would this change if say we went for say 100 sheets?
How would this change if artwork was supplied. What about scanning? Would it be up to you, the publisher, to scan/digitise the images or would it be acceptable that images are supplied, as long as they met a base specification (I know if this was the case, I would be paying a professional to scan my prints)?