وعليكم السلام ورحمة الله وبركاته Its permissible to carry the child while you are standing in the prayer as the Prophet صلى الله عليه وسلم once prayed in Jama’ah whilst holding his grand daughter Umama bint Zainab رضي الله عنهن and when he went for the Rukoo and Sujood he would put her down and when he stood up again he would carry her up with him as narrated by Abu Qataadah and Ibn Rabee Ibnu Abdi Shams in the Sahihayn . عَنْ أَبِي قَتَادَةَ ، أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ كَانَ يُصَلِّي وَهُوَ حَامِلٌ أُمَامَةَ، فَإِذَا سَجَدَ وَضَعَهَا، وَإِذَا قَامَ رَفَعَهَا. Narrated Abu Qatada : Allah's Messenger (ﷺ) was (one time) offering prayer while he was carrying Umama, daughter of Zainab, when he prostrated he put her down and when he stood up he lifted her up . This shows that it is permissible to carry your child during the prayer. However we must be sure that the child is in a state of Thahaarah (not having any faeces or urine or any other impurity on his clothes) as it is a condition for the validity of your prayer. Also the extra movements that may occur because of holding the child is permissible as it has been mentioned in the previous Hadeeth. So if you wish to do this to follow the Prophet صلى الله عليه وسلم then may Allah عز وجل reward you for following the Prophet صلى الله عليه وسلم . ِAnd Allah عز وجل knows best.