IMO, if he submits the 5 in AP CSA and keeps up with robotics, that’s “proof” he can code and he should take the electives he wants.
That said, there is no getting around doing some CS in college as an engineer, regardless of discipline.
I do think that for some of the more “hands on” engineering schools, having the eng/tech/cs electives can help with admission, but those aren’t necessarily the highly selective programs as they are defined on this site.