TL,DR: This seem to be the child actor's Douyin account: https://www.douyin.com/user/MS4wLjABAAAAg6tIodefrzE7jW-aKziW1y1DjYKnhocmqvsjr6c1FCz2w8rwvFn5sXi3tflE9Rh1?from_tab_name=main
Ok, so I decided to take this challenge because I was a bit bored.. I found out that the main guy is called Ai Hong Chen (https://mydramalist.com/people/118217-hong-cheng-ai)
So based on that, I went through his dramas (which are almost all vertical ones), and found the name on mydramalist of the show in your post:
https://mydramalist.com/783716-there-s-a-toddler-at-the-police-station-who-claims-you-re-his-dad
However, it only lists the main actor and actress, and not the child. I found the Mandarin title above on MDL. I used that to find a facebook post in mandarin that also asked about it.
They referred them to the male actor's douyin where he has a video with the child actor dancing:
https://www.douyin.com/user/MS4wLjABAAAADGtLyq_HDeFgr3LQ8UtImpiq_OC8NwZSAy2C9RUXRHVf728c9O6kSusVFYARAAMq?modal_id=7448207231562042681
The male actor Ai Hong Chen mentions in that video that the child's name is Tang Yuan, as he says smt like ""Teacher Tang Yuan, I tried my best.
If you google 汤圆 儿童演员 (Tang Yuan Child Actor) you can find many posts about the child.
This seem to be his Douyin account: https://www.douyin.com/user/MS4wLjABAAAAg6tIodefrzE7jW-aKziW1y1DjYKnhocmqvsjr6c1FCz2w8rwvFn5sXi3tflE9Rh1?from_tab_name=main
You can also search for Douyin 96379108284 as that is his ID number on Douyin.
I do not speak Mandarin, so if anyone has a correction, please update.