When I was a kid, I loved technology and building things. However, I didnt know what an engineer really was or what they did until much later. I recommend that you take opportunities not just to learn about science and technology, but also to meet scientists or engineers. Try to learn a bit about what their work is like, and how they got there.
In the shorter term, Id love to see rovers on Europa and Enceladus. Id like to see a balloon, rover, or even a boat on Titan. Perhaps even a mission beneath the ice of Europa would be in the cards.
I think sending interstellar probes to other solar systems will be of growing importance, as our catalogue of extra-solar planets grows rapidly. The technical challenges to a mission like this will be very novel and rich.
I ultimately hope humans come to live on other planets, in other solar systems.
When I was in elementary school, I wanted to be a chemist. It wasnt until later that my interest in physics and engineering developed.
Our understanding of Earth is very colored by the fact that its the only planet humans have ever lived on. Studying other planets gives us scientific context that will be useful in understanding and protecting our own planet.
Additionally, the engineering challenges of planetary exploration nurtures new technologies that pay off now and in unexpected ways in the future. However, one very expected application is that, ultimately, I believe humans will explore other planets and stars. Robotic exploration is a crucial first step in developing the required technologies.