I would say decide right now if you want the blue books or not. It is totally fine if you do. It will be a different experience if you do or if you don't, and if you don't have a core of strong singers then that might be the preferred way to go. Just choose with or without and there are advantages and disadvangates of either. Just don't try to mix them or please everyone because it is probably impossible and this will save you all sorts of trouble in the long run. I would go with the blue books unless you have a really strong core group and the very strong desire to have it function this way. Otherwise, it is too much trouble. Just be honest and say what the structure will be and people will come or not according to their preferences.