All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
If this is done in order to teach the Athkaar (mention of Allah) and the supplications to the children and to get them accustomed to such supplications, then there is nothing wrong with this.
This is like teaching them the Quran and repeating it for them so that they would memorize it and recite it in a perfect manner. It is a good act, and one should teach them various Athkaar and not only one Thikr.
Since you write to us in Arabic sometimes, we refer you to Fatwa 134255 on our Arabic site about students repeating a verse collectively, and whether or nor this is an innovation (Bid'ah). So, please refer to it.
Allah knows best.