You need to consult a Lawyer before you go live.

The thinking you are using did not work for Napster, Napster argued that they were not in control of how the users shared the content, they were just a vehicle to share it on. They lost in court, so that might be one precedent someone uses to sue you.

I am not a lawyer, and I do not play one on TV, so please contact a lawyer, spend the little money it will cost you to have a two-hour conversation, and make sure you are covered.