Calculus AB will be a slower paced version of calculus in college that engineering and CS majors will take, so it may be better to take it at the slower high school pace than to take calculus 1 in college at college pace (while adjusting from high school to college) after having no math for a year after precalculus.
However, if he majors in business, he may have the option to take a less rigorous calculus-for-business-majors course in college.
Regarding science, has he already had all three of biology, chemistry, and physics (not necessarily AP)?