I'm threatening to host a family dinner but make a Thai peanut dish specifically so my sister and her kids can't attend (too spicy and they're allergic to peanuts)
Why do you want to exclude your sister and her kids?
I don't like them but want to enjoy the rest of my family.
It is rude and very mean to make food that could kill someone in order to exclude someone you don't like.
When you're a kid, you get over all that stuff.
It's not okay to invite everyone in your family except your sister and her kids. You should be more welcoming and try to get along with her.