I think that your age upon finishing a second bachelor's degree might actually be an advantage with most employers: you are more mature, you have worked full time and therefore developed good time-management skills by attending school while simultaneously working a straight job, and you will be very focused on the types of work you want to pursue in your new field. In short, you've already gone through the new graduate adjustment break-in period that I've seen in many of our younger employees. Although returning to quantitative classes like calculus, physics, and chemistry may sound challenging, I believe that your previous good math experience and scientific technical skills (as evidenced by the guidance of your high school instructors to choose an engineering career) will kick in after a short brain warmup period if you give them a chance. Given the time commitment usually required by the first year core courses, you might find it helpful to start out with a single course per semester for the first year to allow yourself a chance to reallocate your time between work and school. Some strategies I can think of for managing your time and getting the most out of your classes would be to block out time on your calendar for studying and homework, joining a good study group, or picking up and working problems in some physics and math review study guides of the kind you might use to study for the SAT exams.
Best of luck!