You don't have to send away for copies. Go to your local Department of Records -- or whatever it's called down at city hall -- and they can connect to other places /print out a birth certificate from another state or whatever. I forget what they call this process, and, of course, they charge an extra $10 for this -- but you can walk out with a birth certificate or marriage certificate in your hand that very day.
I'd argue with the term "preferred name". Your records all use your legal name.
This is something that comes up with our high school seniors every year when they apply for their diplomas: Your name is William, but you've always gone by Bill -- nope, your diploma is going to say William. I remember one kid who went by Carlos, but his birth certificate said Carlo. And a girl who went by Tiana, but her birth certificate said Tiara; she had no idea her real name was Tiara. Diplomas are legal documents, so we have to go with the birth certificate.
That's your choice, but it is easier to bring one document. A document that fits easily in your wallet /a document that's already IN your wallet. And you're talking about keeping up with TWO documents that have expiration dates.
I assume the Real ID will one day become mandatory, so why not get the small hassle out of the way now?