Why not "...esta en la casa de mis padres?"
es because it's an EVENT
Here is a good link to show that, among other things, "ser" is used for events.
I'm wondering why my translation: "at my parents' home" was incorrect?
yeah, I know. "hogar" is home. And "en la casa" is at home. If you want to call your folks' house a home, no biggie, but you'll be less frustrated sticking with "house." ;)
Thanks. I see what you mean :D
Why is El necessary here?
Naturally, the word "Lunch" in English doesn't need to have "The" before, because it's a name of something. In Spanish, as much as I know, Lunch need the word "The" before.