We are doing the same thing for ErlangCamp. We realized we could lower the price point, so we did, as well as retroactively lowered it for those who already had ordered.
I like the general idea, however I would consider focusing it more on being a brainstorming session rather than a lecture. As a Ph.D. student, all my interesting conversations have been with my advisor and other faculty, usually over beers or some other informal setting. I generally don't get inspired during lectures. They are more or less to develop a base of knowledge, not to generate ideas.
It is also a chance to informally reinforce or learn new concepts about specific points of your ideas while you are discussing them back and forth.
To me, that is what a mentor does. Not help you understand a tutorial or what not.