I'm not crazy over Rhys, I think the spelling is unattractive and the sound of it is very "posh" or effeminate. But if you want to use it, I say a classic masculine name is best for a middle name. Some suggestions:
Rhys David
Rhys Edward
Rhys Patrick
Rhys Oliver
Rhys Vincent
Rhys William
I dont' think Rhys and Raven "go well togheter." Rhys is very "posh" and English, as I said and Raen is very goth-girl, something a teenage goth would choose as a screen name or something. If you like the two names to both start with R, then some ideas might be:
Rhys and Rosemary
Rhys and Rebecca
Rhys and Rachel