Actually, for some schools your plan could have a negative in terms of college apps: if you read the fine print some actually say that they particularly look at the rigor of senior year - b/c they are watching out for people who load up junior year and then coast.
And I agree with mathyone: Physics C + Bio (content heavy even with the update) + Calc (AB or BC?) (plus English, Italian and a History/social studies?) is a tough course load for the year that you want the strongest marks- and then there is the time commitment for leadership roles in ECs. With absolutely no disrespect for your son’s ability or energy levels, that is a lot. If he is your first, be aware that many, many kids find junior year the hardest of high school.
Of course, what we are missing is why he is so set on taking 2 at one time. Guessing at possible reasons: to pump up the weighted GPA for academic status within the school? only allowed to take APs from junior year on and want to do show colleges that he is academically able/good pre-med material? Trying to have enough APs to reduce the number of credits needed in college? Trying to skip intro level classes in college? (fwiw, depending on the college, depending on the college and his score on the test, going into a higher level class may be possible, but AP credits do not count as the med school pre-reqs, so physics, bio, chem (regular & organic) will have to be taken again anyway).