This is a tough one. Your dad has really made an effort for you to attend your dream school. For anyone else I would say that a loan of USD 80,000 is crazy for the difference between these two places. Especially when you know up front that you are messing with your dad’s retirement money.
The truth is that in order to be successful in the major that you want, you will have to work very hard wherever you go. The effort to earn the GPA needed to get into the major that you want at UMN is probably no more than the effort that you will need to make in order to stay in the major at UIUC. Unless you have hard evidence from multiple sources that students with this major at UMN are not hired by the same category of employers as students from UIUC, there is no reason to prefer UICU over UMN. Good companies recruit at both UMN and UIUC, and starting salaries for engineers do not depend on where they graduated. Those starting salaries depend on the student’s major and previous work experience from internships.