You can deduct the interest on the PLUS loan assuming interest was paid in 2013. Your loan servicer should have the tax form on their website for you to view.
You can likely claim a tax credit, I think it's the American Opportunity something or other. I believe you have to pick either the interest deduction or the credit, not both.
I will eventually payoff this loan depending on his performance in school.
You probably know this, but you'll be paying it off no matter what if you son doesn't or can't pay. The loan is only in your name and he has no legal responsibility for it.