Sounds to me like a small scheduler should be plenty. Why not RTOS? KISS principle is always good. I would say the question is whether the project is for fun or for work. If for work, I would say if I was your team lead that you should make it robust enough, functional and maintainable, and not spend too much time on it. If you need RTOS to fulfill that - sure go ahead, but I doubt it!
If for fun - go ahead! More experience is better than no experience! 300 line main function sounds like it's time to refactor, though. But RTOS doesn't help you with that, explicitly.
