Nothing is wrong with AP physics your senior year. The important objective here IMO is to follow the plebe's schedule as best as you can and to have the best grades. Even though he's going to have to do the classes again even if he gets perfect 5s on his AP tests if he does attend the academy in the future, it will show the academy that he can handle the subjects. Even if it is in the span of four years, you always want to make sure that you have the AP English, AP Cal, AP Chem, and AP US History.
Other recommendations I'd have is get him into a foreign language class if possible and also a computer or technology class also helps. These are mainly recommended through the Academy and the Admissions likes to see a little diversity with the language classes.
Don't think that it always has to be AP, because there have been candidates in the past who have not had all AP for all four years and they've been appointed. Some didn't have Honors or IB or whatever. Some had basic regular classes and still got appointed. Your son can have an impressive list of AP classes under his belt in his transcripts, but if the grades don't meet the standard, it's practically a waste of time.
I'd take it little steps at a time. Your son still has two more years of high school, and the academy tends to focus on mainly people who are Juniors and up. Two years is a long time, and there is a lot that is going to happen in his last two years of High School. Whatever happens I wish you and your son the best of luck.
PS: DO REALLY WELL ON THE SAT/ACT!!!!!!!!!