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I have an English to German question.

Let's say I show up to a restaurant a few minutes before I think they open, and I ask the owner (someone I already know) "Are you guys open yet?"
How would an informal question like this sound in German? Could I just say "Sind Sie schon geöffnet?"
... or would I have to refer to his restaurant in the sentence and say... "Ist Ihr Restaurant schon geöffnet?"
I'm very confused!