You need to go. No sense in feeling bad....they are your parents! You have helped them out at the restaurant...you could have easily gone elsewhere for a job. Go to school...but do not fook around...as you know its your parents money on the line. If you like it...finish. If it sucks...then just come back and stop wasting their money.
Once you are done with your education...and get your career going, you will be able to help them out again/repay them for their sacrifices. You are an investment to them. Just do not let them down by crapping around with BS classes and partying the whole time. Get yo shit done!