Kudos to you for being pro-active in your high school course selection!
AP Computer Science will be a good course to have on your transcript, as would courses in advanced math and physical science, such as AP Calculus and AP Physics (if those are available to you).
Mechanical Engineering is a "Core Engineering" degree, with math courses consisting of Calculus I, Calculus II, Calculus III and then Differential Equations. In addition to this, you will take coursework in Mechanics of Materials, Dynamics, Statics, and also some courses in Material Science. You will also take electives in areas that you want to specialize in as a career, such as robotics. A good idea would be to look at the degree requirements from the College of Engineering at the University you are hoping to attend.
Best of Luck!