Yes, I would see how first semester goes. If you find you have extra time and things are going well, maybe do a few hours of tutoring or something. And next semester or next year find an on campus job for a few hours a week.
I agree with @dodgersmom in that I would tell them why your are declining the job at this time. As a full time engineering student and without ability to work around schedule and exams, you cannot work there during the semester.