While I tend to agree with Glenn and Sam with regards to encouraging people to follow their passions (I surely did just that), I would like to offer a counter-argument for the sake of full-disclosure and discussion.
There are MANY ways in which a young engineer, while working towards their degree or working in industry, can follow their passions outside of their daily job. You have found an avenue to do just that, through robotics clubs, teams, or organizations available in your school or in your area. Those things will exist wherever you choose to go to school, and would still look great on a resume, if you were working on your Mechanical Engineering degree. Many engineers are "tinkerers" or hobby-enthusiasts outside of work because they like to do things that are not within their day-to-day roles within their company. That's a pretty stereotypical engineer, someone who works for a living and plays in an engineering realm outside of work because that's what we love to do. Not everyone will land their "dream job" in engineering, its something you might have to work long and hard for once out of school.
Mechanical Engineering is great because just about every type of engineering project requires ME-minded folks to play a major role. It is a wide-field degree and teaches you in general how to solve problems, be a critical thinker, and research and design and assemble and improve all sorts of things.
Mechanical Engineering is a much wider field in industry, and thus it has a much larger share of the workforce (and job openings) than the Robotics Engineering field, which is more of a specialty degree.
I'm not saying to choose Mechanical over Robotics, but you need to carefully weigh the pros and cons of each. If you are looking to be able to live just about anywhere, have a better chance of getting a job in your field right out of college, and be a part of just about any type of engineering work, Mechanical Engineering is the logical choice. And if you choose that, you can still work towards a ME career focused on Robotics, and you can always choose to use your free time to "play" in the realm of robotics just as you are doing today.
Don't loose that passion!