I wouldn’t double up, and not in that order.
He should take AP Bio junior year (with apes if it makes sense for him because he likes the subject, because it’s an easier AP to add to AP bio, and because there’ll be some overlap with AP bio which will reinforce learning in both - but he shoukd not take it solely 'because it’s an AP ’ since it’s generally seen as a weaker AP and won’t help It’s admissions for a kid who’s taken AP bio and AP physics).
Then, senior year, AP physics, which I assume is AP physics 1 or 2. If AP physics c, has your son taken honors physics ? Also, he’ll be glad to have the study hall that year.
Finally, more important than the number of AP 's, he needs to take one each of bio, chem, physics (honors is fine), then add one AP - unless he’s not planning in majoring in anything stem -y or to be premed, in which case there’s no need to double up in science.
BTW doubling up is NOT expected.