High school computer science classes are often pretty worthless and I don’t think they are viewed as high rigor by most colleges. I could be wrong as my view of it is a few years old.
One option to consider option might be to do an online CS course during the summer and Spanish III at high school. There are excellent CS related courses available online, and the subject lends itself to online and self-paced learning better than a third year level language course.
This way it wouldn’t matter if the course was “accepted” for credit or not, it would simply be something your son is doing because he’s interested in the subject. Taking intro CS for credit at a community college would be another option.