I think one way you can avoid it being a "gift" is if your parents put the money in a joint account with you with 1) your parent's names, and 2) your name. This way, in terms of administering the money, it'll be easy for any of you to add or withdraw from the account. Also, it avoids the definition of "gift" (and therefore the strict IRS definition of gift) in the sense that there is a string attached- they're retaining some control over their money. You can then pay the tuition out of the joint account and if any questions ever come up down the line, you can at least point to the fact that their names were on it and you were only using it for tuition.
Personally, I think putting the money in a "Risk Free" CD is the best way to get at least some interest on what you don't spend (probably less than 1% or close to it). How the Risk Free CDs differ from traditional ones is that you can withdraw from them at any time in case you need money immediately, but they have a higher yield interest rate than a savings account (which these days is close to 0.5%). I know Bank of America has one of these types of CDs, I don't know if credit unions or other banks have it.
If you're absolutely sure of when you're going to withdraw from the account, then you could get a higher interest rate by locking some of the money in higher rate CDs (What
@InvestingDoc says above). But if you end up needing the money for an emergency, then you'll pay a penalty which often negates any benefit the higher interest rates have.