I love
Ceridwen (though I do prefer
Cerridwen, personal preference). I also enjoy the witchy, goddess, writerly stuff about it.
Dwen,
Wen or Wennie could be a cute nickname maybe. Although, I pronounce it more like "KEH-rid-win", so Win,
Dwyn,
Wyn or Wynnie would make more phonetic sense to me. But it's spelled -wen, so...
Cerridwyn would be neato too though. If you're ok with tweaking spellings.