What are the criteria for washing hands when touching a child on parts of the body that are usually covered? I.e., what age does one have to be machmir, are we more lenient with regards to children because often they wear clothing with more exposed skin, etc.
The criterion depends on the age of the child and is this part of this age child usually covered or uncovered. If it is the norm for a child of such an age to have this part exposed then it isn’t considered a covered place, but if the norm is that this part is covered then it is considered a covered place. For example young children often wear clothing without sleeves, or short pants, therefore until the age that the child won’t wear such clothing, if we touch such a part, we do not have to wash our hands.
Halichos Shlomo Tefillah 20-16.