There are lots of ways you can work with youth (and lots of other ways not to have a desk job). I would definitely recommend looking into majoring in social work in college - there will be lots of opportunities to intern with youth organizations then and you can get a feel for them. Another great way to figure out what you might want to do is to be a youth leader now! Get involved with a local youth organization - attend, apply to be on their leadership board, etc. And when you're there, watch the staff who work there. If some of them have jobs that look like fun to you, ask to speak to them about their jobs. Ask them what a typical day looks like for them. Ask them how they knew this was what they wanted to do. Ask them about their education. Those are all great ways to get started.
And... you've got TONS of time to figure this out!