No need to bring anything back to Anshan everything you need you can buy back home BTW there's a Supermarket name 佳梦达超市在太平 鞍千路 they carry all kind of western stuffs I was there a few times when I was back in Anshan
U can buy ur winter coats in China, they are cheaper n serve the purpose. Also save carrying them back n forth. Keep them with ur mom in law so u can use them whenever u need them.
Why do you want to purchase toothpaste and such at Costco? I last visited China in 2018 and there were lots of Western brands in Chinese supermarkets and at lower prices than here in California.