Several times at funerals in the Kingdom Hall I have seen disfellowshipped relatives of the deceased and I have always gone out of my way to give a huge hug and offer my condolences. They have always seemed to appreciate it, and no one has ever approached me about it. I just think it is the right thing to do under the circumstances.
However, the regular meetings are another matter, as some have noted. If the disfellowshipped one is at a regular meeting, they probably are trying to get back in, so they may not appreciate the attention.