Until the age of 6 the father is obligated to feed, clothe and room his children. And it is enforceable. Then until 13/12 he should still do it.
But after 13/12 he is only obligated to do it as tzedoko (S"A E"H 71)
But to me it seems Rabbi Moshe Feinstein was only talking about support of food (this is an obligation to his wife to give her food to support guests), but that the father is not obligated to clothe and room his children after 13/12 (except as tzedoko)
Please explain if I am wrong and bring evidence to that
PS can someone explain why the obligation to give wife food to feed guests is not in the Rambam or Shulchan Aruch?