At most schools, it is very difficult to transfer into CS. Some schools do not even allow it.
In addition, the admission rates for CS are much lower at many schools. So your son would have a tougher time being admitted to CS. There are a handful of schools where business would be a tougher admit. UPenn Wharton comes to mind.
It’s probably best to figure out what he really wants before making a school list and applying.