Male: Desmond I'd prefer, but failing that either of Jack, Hugo/Hurley, James, John, Jin, Charlie, Michael, Walt, Boone or Benjamin
Alternatively, we change our surname after we get married to 'Eko' and don't give him a first name, so he's simply Mr Eko
Female: Kate, Sun, Claire, Shannon, Rose, Ana Lucia, Danielle, Juliet, Elizabeth/Libby, Penny
We could just have enough kids to have the full lost names if you wanted