Maeva and Sullivan are really nice together!
Some other girls ideas:
Eh, I liked to maintain that the "general public" has crappy taste in names, lol. ( And if this forum was BG, then this is especially true!)
I love your sons name! Truman, Calder and Rafferty are all great and go perfectly with Sullivan. Edison was what came to mind immediately for you.
How about Raphael? You said you liked Rafferty, and they are very similar, both w/ nn Raph/Raf. Or you could spell it Rafael. Just a thought!