It's enough to tell your parents you'll be fine if they don't come for graduation. But then let them decide if they want to come--they may wish to be there, for themselves, to revel in your success and share it with you. As you have noticed, it's very special for them, to see what you are accomplishing. Let how to accomplish what they wish be their worry. You might just focus on yourself, and what you need to do to pass your final courses. As someone said, grades aren't all that important at this point. Worry about what you can control--yourself and the tasks you need to do to finish--and try not to think about the things you can't. Like how your parents can achieve their goals. Take care of you, for you!