I love the idea of honoring your mom's family, and I like the look of Raphan. I'm really not loving RAY-fin, though. I find it non-intuitive; I want to pronounce names that start with Raph- or Raf- with a RAH or RA (like cat) sound. I also think RAY-fin trendifies the name. I mean, a "two-syllable name with a long A and an -n ending" perfectly describes the most common current trend in boys' names.
With a different pronunciation, I think Raphan would be okay as a first name. I'd save RAY-fin for the middle position. FWIW, I think Rahn would be a handsome middle name, too.