As others have said, you really don't need to worry about it, jmejia. The AMCAS itself, I believe, says that what you write in that section is by no means binding. They want to make sure that you receive your degree, and I suppose they'd like to see a continuation of your hard work from the past three & 1/2 years, but if you wind up choosing different classes, it really isn't going to make a difference.
If you're very concerned, you can send an update letter to the admissions office. I was in a similar situation. . .I originally intended to take several classes for a minor this semsester, but then decided instead to take a graduate school chemistry class, continue thesis work, and use an independent project for credit. The admissions offices didn't have any problem with this.