It sounds like you want to do... exactly what Google Plus was designed for you to do?
Sharing is opt-in on Google Plus, not opt-out. There's no public wall for everyone to see and post on--you have to manually select which people you want to share an item with each time. You can group them into "Circles" for convenience.
(I'm not shilling for Google+, I haven't used it in months myself. And I have no idea how Reader integrates with it, *and* it is of course annoying when you're shoehorned into using something you're not interested in. But it sounds like you complained about the one thing Google Plus is specifically designed for--sharing with small groups of people.)