snowy,
your aunt took the children for a reason. she may not yet be able to say the words, but she knows something is terribly wrong.
i guess i think that as members of society, if we see a child in danger, it is our place to contact the authorities. unfortunately, "name-calling" as dstructive as it is, is probably not cause enough to intervene. that doesn't mean, though, to not make the call.
i do agree with the others that speaking to your uncle is crossing a line where you do not belong.