Dictate
One might think that since the Xiang family found Justin, they'd hold a grand birthday party to announce to the whole world but things were not like that in reality. In fact, Xiang Weimin's original intention was to do big things but while planning the party he changed his mind. He knew Justin wouldn't be comfortable with it.
No, it's right to say no one will be comfortable with it. From Grandfather Xiang to Raelle, no one liked going to socializing events. Xiang Wai and Xiang Weimin didn't have any problems with big crowds since they practically lived with a bunch of men in the barracks but the rest of the family liked the warm and cozy atmosphere.
Apart from that, this was the time when he decided to tell Justin about his identity and he felt like he first needed to talk to his son before announcing to the whole world. Anyway, Justin would be more comfortable with people he was familiar with rather than seeing so many unfamiliar faces.