Expelling these people from the family would prevent all of this from happening. Not only would it preserve the lives of his son and nephew, but it would also save the Cao Family.
Furthermore, taking a step back, if the Cao Family submitted to Li Daofeng, and by any chance the family got implicated and wiped out, having these banished sons around would at least leave a few surviving bloodlines for the Cao Family.
One has to admit, ginger really is spicier the older it gets!
Chapter 88