1. Have him call, not you.
2. Maybe have the first call to be to either his (a) research advisor( if applicable) (b) advisor (sometimes departments assign their undergrads an advisor in the department who just helps them plan their time at BYU) (c) undergraduate coordinator.
3. Be prepared to hear, "you are crazy, you can't be in two places at once," or, "this is a risky plan. Students who do this struggle."

Anyway, best of lucj