Is it obligatory for two daughters to perform the duties of hospitality for their father's guests, and is their refusal to do so considered an act of disobedience?

The two girls must obey their father in serving his guests if no harm results from it, for obedience to parents is obligatory in matters that benefit them and do not harm the child. Honoring parents and being good to them are among the greatest causes of Allah's pleasure and entry into Paradise.