Force Share on Register

This is sort of a complex questions that I need some guidance on. Hopefully I can use a combination of the plugins here to accomplish this with only a little coding. I have a site with a lot of private content. I want this content to be available only after the user does 2 things:
1. registers as a subscriber with email and password (no other info required)
2. shares the site on Facebook

Is this doable with existing plugins? If not, any suggestions on which building blocks I should use and where I will need to code? I know this is a pretty broad question so I appreciate any and all advice - thanks!