I completely agree. Using option 3 has its own set of con's, and this is one of them. Many Users have been misused/tricked in the past and don't like the idea of associating a new (aka unknown) App with their Social Media Accounts. For all they know the App will steal their data and spam their friends. This is in line with some of the feedback I get when validating with potential customers.

You may have hit a sweet spot there with option 2. Keep us updated! An interesting Metric would be comparing the Bounce Rate between these options above (ala A/B Testing).