Q: Is it okay to say, “The Smiths and we go to the park”? I know there are better ways to say the same thing, but I’m wondering if this is grammatically correct.
A: As a compound subject, “The Smiths and we” is indeed grammatically correct. But it’s not syntactically common (syntax deals with word order).
The common word order, as you’re aware, would be “We and the Smiths go to the park.”
Why does that sound more natural? We did a bit of digging without success, but we suspect a scholarly paper or two is lurking out there with the answer.
The subject in a sentence like the one you cite should never be “The Smiths and us” or “Us and the Smiths.”
Those constructions would be used only as objects: “Come to the park with the Smiths and us.” Or, “Come to the park with us and the Smiths.”
As part of a compound subject, a pronoun is always a subject pronoun (I, we, they, he, she).
As part of a compound object, a pronoun is always an object pronoun (me, us, them, him, her).
Sorry we couldn’t be more helpful about why “We and the Smiths” sounds better than “The Smiths and we” as a compound subject.