Luca is popular on an international basis as well as in the U.K., up to you if that's a good or bad thing. Maybe a bit dull?
Arlo is a trendy name that will date.
Raphael is nice, it's not that unusual so I don't think your son will have problems with it. Is he likely to be fair haired/blue eyed? I always think it's a strange name unless baby is a bit olive skinned.