Yes, you need approval to change your major. It typically is not an issue to change within the Tech wheelhouse. Here is something to think about if you want to go rated. There have been years that certain engineering majors, unless they are the very top they will not be allowed to go rated due to AF needs. A few years back it was EEs than it was MEs that many had to go tech nonrated. Not the sword also cuts the either way if you want to go rated with the ultimate goal later down the pike of becoming a test pilot. One of the things they want for TPS is an engineering degree.
Engineering is very difficult, and jmpo, but I don't think many hs students realize the difficulty in obtaining this degree, especially their freshmen year. Major in something you are passionate about, not saying I disagree with switching it to degree offered IS, but make sure you also want to attend that school because not liking the school and the major, but doing it to save the money may result in a lower cgpa and in the end it may mean you will not be picked up for SFT. Your first three semesters are the GPAs they will use....mess up that first semester, is 2.5 than it will be hard to get to the avg cgpa of 3.1 for selection