I found this article and absolutely love it...I can't send it to all my guests but I will send it to all my kids. I particularly like the rules on "conversation" and "trouble shooting:
http://www.bonappetit.com/entertaining-style/holidays/article/thanksgiving-etiquette-guide
and...I totally agree that any of the sibs bringing up unpleasant topics is not teasing or poking fun, it is harassment. Say something nice or don't say anything at all.
Good luck! It is anxiety provoking!
Echo