I think its nice as a mn. I know it isn't the traditional spelling, but as its a translation of a Greek name, surely it is as valid as
Charis? I don't know, correct me if I am wrong.
I think it would be a great story to tell your child, a lovely way to honour your dad and it has a nice meaning. If you still felt uncomfortable with it, would
Charis still honour? I prefer that spelling usually, but in this case, honouring and the story behind it makes me like Karis more.