Your classmate is getting married, so you have no time to attend. It is ok to give gifts a few days in advance. If you have a good relationship with this classmate, you have been in contact and getting to know you back and forth. It's okay for someone who has to give it to you not to be blessed, and your classmates can accept it. If you don't get along with this classmate at ordinary times, there will be no good relationship. Generally, you can find an excuse not to participate.