A. When a hindu male died without execute a Will that property shall be distributed equally between the class I legal heirs i.e, wife, mother and children.
B. In your case, only khatha has been transferred to mother name, doesn't it mean that property right has not released from their children, Hence all the 4 male children signature on Sale agreement and Sale deed at the time of registration is mandatory.
C. Therefore, all 4 male children along with mother would be considered as lawful owner of the property. Hence, 4 children and mother name must be mention in the Sale Deed as owners.