@thecabinetbarn Haven't been there, yet, but I will have to in the somwlewhat near future.
If it were me, I'd explain to my kid(s) that sometimes people don't say nice things. It hurts but it's that entirely their fault. They learned it from somewhere and they're wrong.
I'd tell how I got over it even though it initially also hurt my feelings growing up.
These kids are ignorant and can't tell a Chinese person from a Japanese, a Japanese from a Korean, a Korean from a Vietnamese.
In my case ot was easy for me because I am Viet and kids called me ching chong, Jackie Chan, Jet Li, etc. And I thought how these kids aren't so smart. I'm not even Chinese. But, then again Jackie Chan is a cool dude!
So, kind of embrace the Asian culture. They can say whatever they want because they're wrong and just be a bigger person.
They may think "ching ching ling ding ting" or whatever is Chinese, but when you actually listen to Chinese talk whether Mandarin or Cantonese, it doesn't sound like it and it's those kids who are looking real stupid.
Ignore them and don't give them ammo. If they see you are bothered they'll keep doing it. Don't retaliate to make it worst, but that also doesn't mean if things get out of hands that they can't catch these hands...
Idk if this will help, it's just a personal anecdote but I will definitely use with my kids.