With those examples though, if the State did away with the legal recognition of marriage, do you believe it all of the sudden wouldn't require education for children? Same with firearms ownership - the "dangers" of firearms apply whether or not two people are married. The taxing example is your best one, but the State taxes people differently regardless - income v. capital gains, income tax differing on income level, etc. I don't follow how marriage specifically changes the powers of the State - at worst, marriage merely gives a rationale for the State to do certain actions. Other reasons would be found to commit those same actions if marriage was suddenly removed from the equation.
Are you seriously arguing that my wife and I, my mother, father, and our grandparents aren't a family?
No. You'll notice in that arrangement, YOU are the children which make it a family. However, I would say looking at just you and your wife that you are not a family. You are a married couple who have the potential to become a family, through bringing new life into the world. No gay "married" couple can ever have that potential.
Hope your evening was restful.