Apparently it’s happened already and one Cynthia Lindenmeyer officiated.
Google says Lindenmeyer is a former Army Chaplin and an ordained minister in the United Church of Christ, I believe that’s Obama alleged denomination.
Yes, Obama is a member of a UCC church. I got married in a UCC church in 2009, since my wife chose the church. I was surprised when I later learned that some UCC pastors support same-sex weddings.