At what age should one make sure that one’s children’s hands are washed (netilas yadayim) after awaking in the morning? Should one wash the hands of one’s baby or infant?
Several poskim write that one should wash hands for an infant, wherever there is a possibility that his hands will come into contact with food. See Peri Megadim (4, M.Z. 7), and see Shulchan Aruch Ha-Rav (4:2), who writes that although there is room for leniency concerning infants, it is preferable to wash their hands, too. See also Ben Ish Chai (Toledos10) and Kaf Ha-Chaim (4:52).
For very small infants, for whom there isn’t any clear night or day (in terms of sleeping patterns), there is greater room for leniency, but once there is a clear night, one should preferably begin to wash hands.