With or without the 'í', Little Martín is going to be called "MAHR-tən". He probably won't even bother correcting people, after a while. Sorry.
I like
Martin, though it's not a favourite. It reminds me of my 3rd favourite English teacher, it was his first name. Nothin' wrong with
Martin =)
Middle names for Martín:
Martín
LukeMartín
IsaacMartín Théo
Martín
Olivier
=)