بسم الله الرحمن الرحيم

It is not necessary to simultaneously shave the child’s hair with the sacrifice of the animal. Rather, one may shave the hair before or after the animal’s sacrifice according to one’s convenience. It should not be considered necessary to do both simultaneously as is famous among the uninformed.

Muftī Salmān Mansūrpūrī

Kitābul Masāil Vol.2 Pg.343