Difference between Attachment and Goals
Technically, you could resolve this either way. As long as you can completely convince yourself to take a stance and forget the other alternative, you'd be fine.

However in Buddhism we are advised to try and maximize the positive qualities of mind. So if one of these choices makes you more motivated and energized than the other, you will probably do better long term by going that way. 

Now, regarding your parents, in this case you're not violating any ethics, except their expectations of your life, which is the domain that you own 100%.

Regarding goal vs desire concept, in Buddhism it is the blinding desire/craving/lust that is recognized as a danger, for obvious reasons. Yours is not like that. Also, a type of desire that we think about but never fulfill or can't fulfill, leads to suffering. Yours is like that at the moment, so the most Buddhist advice would be to either start fulfilling it or to drop it. Staying in this limbo is definitely a case of generating suffering.