My personal opinion is that if you really like sports you should keep at it. If you really have to choose between sports or an engineering club (You could maybe do both!), then choose the one you think you will enjoy the most. You don't want to miss out on doing the things you enjoy during your high school years, and sports can be very valuable both for your health and for learning to cooperate with a team. Engineering clubs can also really help give you a head start, but if you don't think you will enjoy it for any reason then it may end up being a waste. You might want to review this article on cultivating life skills to give you an idea of other things you can do.
The program at U. of Minn. sounds like a wonderful opportunty. While I am not familiar with it myself, the chance to really expand your math abilities in middle and high school is fantastic. If you really like math then learn as much of it as you can early. You'll remember it better later if you learn it early, and it will be useful to you for the rest of your life. Good luck!