If I were a grown up, I would be a software engineer. I would design apps for mobile devices and computers. I have already designed a game (In real life) and I would most likely be drawn to game design. I think that I can sort of understand what draws a teenager to a game, such as excitement or action. Some applications I might design are things like Google Maps, but that have live satellite feed from anywhere. I might also be a risk management analyst, since I love math, algorithms, the stock market and currency, and risk. I would teach kids how to program and design apps and games.
In all, being a grown-up would be rather math-centric.