Should be, "We are doing well" -- strictly speaking, "We are doing good" is incorrect English here -- or maybe colloquial English is a better way to put it.
As others have pointed out, "We are doing good" is shorthand for "we are doing good works" or "we are doing good things", as Whitey Bulger might have said, as he and his buds walked awy from a shot-up car.
Don't downvote me, I'm just the messenger here!
But that is not the question. It is like if we ask Wie geht es? and we answer Es geht mir gut...in this case though it is an answer when more than one person is being addressed ..I think of the question "Wie geht es ihnen?" when you are perhaps addressing a husband and wife and the husband answers for both.
What makes it correct is this: Uns - dative/accusative pronoun: this indicates that it is being used as a(n in)direct object. // Geht - 3rd person, singular conjugation of the verb gehen. // Es - 3rd person, singular pronoun in the nominative case: it can only be used as the subject of a sentence. // Gut - An adverb meaning "well" (in this case it is an adverb, whereas it can also be a predicate adjective). // Because these words have such a specific use, their order isn't very important as it is in English, and the order of "Uns geht es gut" just so happens to be the preferred order in German!