Hello everyone

We are a white couple from New Jersey. Our 8 year old son is light skinned and our 7 year old daughter is dark skinned. They are half siblings. They are gorgeous. So far so good. We have not seen any overt signs of predjudice. It's more in the form of sideway looks and people turning away. That;s fine because my kids don't notice it yet. I know that one day someone,maybe another kid or maybe an adult will call them the "N" word. How do you prepare your kids for that. I have never experienced it which makes it even harder for me to prepare them. Does anyone have any suggestions?