This made me smile because Peter Mark is a huge chain of hairdressers in Ireland. So if there is any chance you will live there in future, just make sure you haven't used 'Peter Mark' as the full name.
I'm not wild on either name and together with Sarah, they sound a bit too 'safe' to me. Someone else suggested Luke and that led me to Matthew, keeping up an evangelical theme - I think Matthew and Sarah sound lovely.