You could have him progress through theoretical physics and learn and practice the needed math along the way. For example in electricity and magnetism taught at the level of Jackson, one learns about solving partial differential equations and special functions. Quantum mechanics uses that math and also linear algebra, and there are applications of group theory. Computational physics requires numerical analysis and programming skills.

We are a two-

Arfken household, but all the same.... argh!

(Mind you, it would be cool if someone in the household actually read all of the three volumes of Feynman's lectures on physics we have lying around, I have to say. So yes, maybe.)