Are your parents coming for your graduation? Is the usage correct?
"Are your parents coming for your graduation" implies that the parents are elsewhere (as in, they live out of town) and are traveling to where the graduate is, with the reason for the visit being the graduation ceremony. Consider someone who went away to college and upon their graduation, their parents come to visit and attend the graduation.
"Are your parents coming to your graduation," on the other hand, seems to be asking solely about the graduation ceremony itself. They might be local or perhaps they were visiting but it was unsure if they would be attending the ceremony.
As an example: my niece is graduating from college in Southern California this June. She knows that her parents will be coming for her graduation (as well as to help her pack up her stuff.) Next year, her brother will be graduating from high school. Her parents will definitely be going to that ceremony as well; the school is nearby.
To sum up, for provides the reason for the coming; to indicates the destination.
Hope this helps!