We had a party for our daughter when she turned 100 day-old. We had a cake that said "Happy 100th day", fruit, dumplings and so on. We invited some of our close friends and their family. We also put on a daughter a traditional Chinese silver lock on that was given to her as a present. We limited it to 2 hours and it was fun. In the invitation, you can explain a little bit that this is a Chinese custom in case non-Chinese friends are unfamiliar with it.