I'm thinking Cartney or McCartney
as a homage to
http://en.wikipedia.org/wiki/File:Pa..._in_Prague.jpg
I have looked up 'Mac' on one baby names website, and it says it is a Scottish name meaning 'son'. It can also be short for 'Macaulay', which means 'son of righteousness'. I can imagine that could be his full first name. Does it suggest he os of Scottish heritage perhaps?
One more thing- since it has been confirmed that his parents are divorced, I recon Mac's current surname is his mothers.