Most of the time Ean would take your name since traditional the child takes the last name of the father. I personaly would give my child the last name of the father but that is for you and the baby mother to decide. you can always use a hyphen

Let me just say I know a girl who named her son the same name, but spelled it Ein, and the baby isn't a year yet and she hates people mispronouncing it. Just food for thought.

As for last name, hyphenate if you can't decide.