MiriamCecilia is gorgeous. I love Mae, I think it's so cute, and I don't even mind it as a middle name despite it being fillerish. But it sounds kinda tacked on at the end of MiriamCecilia. Still, I think it stops MiriamCecilia being too stuffy, so that evens it out.
BUT can I just say I'm very jealous you get to use Miriam (well, on the right sex)! I'd love a little Miriam.