Stay in the band! I am not sure when you will have another chance to play in a band so you should enjoy playing the oboe. I assume you have good grades already and a good SAT/ACT score. So at this point you should just make sure to keep your grades up.
You can always take more classes later. I am not familiar with GA tech admissions, but I do know that at USC we appreciate a well rounded future engineer. I am sure most schools will also value your broad interests.
Good luck and best wishes,
This can be a tough question and there is no "right" answer. I will be biased in my response since music/instruments are an important part of my family's life and I believe in the many benefits of music in education, brain development, and overall creative thinking. The oboe is also a unique instrument that not many people play so it sets you apart. However, balancing activities is a lifelong challenge and you have to determine what is right for you. If possible, I would try not to give up the music, but keeping up grades and preparing yourself for the academic challenge is important.