Children Affixing Mezuzos

Question: Our eleven-year-old son asked if he could fix the mezuza onto his bedroom doorpost. Is this permissible?
Answer: The Shulchan Aruch (YD 291:3) writes that children are also obligated in the mitzva of mezuza and we should train them (chinuch) to affix mezuzos on their doors.
R’ Yaakov Yeshaya Blau (Chovas Hadar 1:25) explains that the Shulchan Aruch is clearly referring to a house that is only inhabited by children. If the child is able to, he or she should affix the mezuza, though doing so is only a mitzva derabanan of chinuch. He questions whether an adult doing so on their behalf would recite a beracha or not.
R’ Avraham Dovid Wahrman of Buchach (Daas Kedoshim 289:2) writes that if a mezuza falls on Shabbos, one can get a child to affix it on Shabbos. Nonetheless, in his notes (Gidulei Karka) he questions whether children can be trusted to have the appropriate intentions as they affix them.
R’ Eliezer Waldenberg (Tzitz Eliezer 14:75:1) notes that there is a machlokes as to whether children may affix by themselves or not, and concludes that they may not affix mezuzos. He explains that even the Shulchan Aruch means that children should have an adult affix the mezuza on their room on their behalf. If a child does hang the mezuza, it should be removed and reaffixed by an adult.
In conclusion, children should not affix mezuzos until they are bas mitzva or bar mitzva.