I don't know as I'd call it trashy. To me a t4rashy k name would be like Kayeleighey or Kaydince or Karringtynn or Kyndall. I have to say I don't care for the name, either Carys or Karis, because it immediately makes me think of caries, or cavities. But it's not the worst you might do.
Although, if it's what your dad wanted to name your sister, it's kind of a stretch to say that using hte name is honoring your dad. Your sister *might* pull that off, but it seems like you'd be trying to hard to honor somebody and the name links you to your dad by only a rather thin thread.