Senior year of high school is stressful. Sometimes it is valuable to allow a student to reduce their stress level a bit.
One daughter did exactly what you suggested. She skipped one AP exam her senior year of high school. The only consequence was that she did not get AP credit at the university that she attended. She still graduated in four years slightly under budget and with a very good GPA in an appropriate (for her) major.
But I would have your son call admissions at the university that he is going to attend and make sure they are okay with this.