Several major Aĥaronim write that it is important to ensure that even small children wash their hands in the morning. Even though they have not yet reached school age (gil ĥinukh), since they touch food, their hands must be washed so that the food is not damaged by the ru’aĥ ra’ah on their hands (Ĥida; Pri Megadim, Mishbetzot Zahav 4:7; MB 4:10). Additionally, there are some who practice the extra-pious custom of washing even a newborn’s hands (Ben Ish Ĥai, Toldot 10), for by doing so, the children are raised in purity and sanctity.
However, in practice, most people are not strict about washing their children’s hands three times after they wake up, because according to some prominent Aĥaronim, ru’aĥ ra’ah only lingers on the hands of girls who are at least twelve years old and boys who are at least thirteen. This is because the spirit of impurity affects those who can connect to holiness and act to repair the world. Hence, the ru’aĥ ra’ah does not rest on the hands of gentiles, for they are not obligated to perform mitzvot. Similarly, ru’aĥ ra’ah does not rest in full force on the hands of children who have not been initiated into the duties of mitzvot. Still, there is a mitzva educate minors in mitzva observance, and once they start connecting to mitzvot, ru’aĥ ra’ah lingers upon them a bit as well. Therefore, from the time they reach the age of education and are capable of comprehending how to wash their hands, one is obligated to educate them and accustom them to washing (based on SAH 2:4:2; Eshel Avraham [Buczacz] 4:3; Tzitz Eliezer 7:2:4).
In conclusion, there is a mitzva to habituate children in netilat yadayim from the time they reach the age of education, and it is an obligation to wash their hands starting from the age of mitzvot, meaning twelve years old for a girl and thirteen for a boy. Some are strict and wash their baby’s hands from the time he touches food (MB 4:10). Additionally, there are individuals who enhance the mitzva by washing their baby’s hands from the time of his brit mila or even from birth, for even then Israel’s unique holiness begins to appear (cited parenthetically in SAH ad loc.; see also Kaf Ha-ĥayim 4:22).