Will it be bad luck to drop a cup in front of the god of wealth and Guanyin?

No, because the god of wealth and Guanyin are both merciful, and Guanyin is still merciful, so it will not be normal, not to mention that you are unintentional. If you want to throw cups at the god of wealth and Guanyin, it will be serious. -in a word, it's over without intention; A deliberate mistake will bring trouble to III.