Family Secret Keeping Isn't Easy

I've been holding onto this secret about my grandchild's little mishap in school. She accidentally knocked over a vase in art class and got paint everywhere, including herself. I didn't want her parents to worry or punish her too much for something so silly, but now it feels like a weight on me every time we talk. Why did I think keeping quiet was the right choice? Is it too late to confess and face the music?