Here's my suggestion: Since you're in an electrical engineering class, you should be able to research it easily, and it'd be good practice. Just run the 12V directly in and have a 5V limiter in parallel. You'll want filtering to eliminate noise, but you should be able to build a plenty strong enough power supply off of a few transistors, some zener diodes, and stuff. The only issue here is heat and impedence of your supply. It'd be good practice.
