Me and wife are taking care of our nine year old nephew. Could my wife give him a hug? Could she touch him (I.e. to cut his nails)?
Although it is better for you to cut his nails, she may cut them, because it is not a touching that involves chiba or a relationship, rather because of a bodily need. However, she should not hug him, as this is because of chiba and not allowed.
Even Haezer 21-7, Igros Moshe Y:D 2-137, Halichos Bas Yisroel 7-10, Poskim.