Question: I have noticed that certain shuls honour children to sing anim zemiros and open the aron beforehand, while other Shuls don’t. What is correct?
Answer: To emphasize the holiness of anim zemiros, ascribed to R’ Yehuda Hachassid, we open the aron hakodesh while singing it. The Bach (OC 132) mentions the minhag to sing it daily, though most shuls sing it every Shabbos while the Vilna Gaon held that it should only be sung on Yom Tov (See Nesiv Bina 2 p260).
Due to this, R' Ephraim Greenblatt (Rivevos Ephraim 5:237) and R’ Moshe Sternbuch (Teshuvos Vehanhagos 2:81) hold that it is inappropriate for a child to lead anim zemiros.
Nonetheless, R’ Shlomo Zalman Auerbach (12:96) held that a child may do so (See Ishei Yisrael 36:n196). Many shuls follow this, especially as they want to encourage child participation at the end of davening.
Many expectant husbands follow the Chida (Avodas HaKodesh, Moreh Baetzba 3:90; Yosef Ometz 57) who writes that the local minhag was for expectant husbands to do pesicha in their wife’s ninth month as a segula for an easy birth (See Kaf Hachaim OC 134:12).
Others quote the Birchas Ephraim (60) who writes that he heard that the Rashba held that the minhag was for husbands to do pesicha for anim zemiros (rather than to take the Torah out) from the seventh month.While the Mishna Berura (147:29) writes that a child shouldn’t hold a Sefer Torah, this shouldn’t apply to pesicha where the Torah isn’t removed.