My experience and the experience of others I know who’ve worked for federal judges is that so few cases actually have any overt or clear political implications that it really doesn’t matter much who you work for.
The judge will also have another clerk or two. Presumably if your kid has an offer, he’s met the judge and gets along with him/her. So there’s an opportunity for informal splitting of the case load (typically one law clerk gets assigned to each case although the chambers can vary).
In all, if it is a very good clerkship/opportunity, nothing that will happen there in terms of challenges to a belief system that has not already happened 2-3x in law school.