Am I doing the right thing?

No, you did not do the right thing in regards to the kids. Frankly, it sounds like most of the adults involved here are acting childish, but there's no point in punishing the kids here and not allowing them to know their aunts and uncles. This sounds like some incredibly simple thing that has evolved into something incredibly childish, like turning a molehill (facebook) into a mountain (telling the uncle not to have anything to do with the kids). Someone here needs to be the adult and iron all this out.