The blood deal is pretty simple. A few years back, they changed the punishment for accepting blood from disfellowshipping to disassociation. That means that they no longer 'sanction' someone for taking blood; instead, they claim that anyone who taks blood has voluntarily withdrawn from the organization. Different words, exact same effect.
As for children being "members", I don't know the exact deal, but here's a guess:
In the United States, Kingdom Halls are frequently owned by local corporations. The "membership" of these corporations is defined as all baptized publishers in the congregation, 18 years of age or older. So children can still "participate" by being baptized, preaching, and even facing a judicial committee; but they're not technically "members."
I don't know if that's how it works in Bulgaria as well, but I would guess it's some word-game like that.