Those are good characters. I like the premise it sets, and Father Luca makes sense for you as a GM. You could go with both characters, too, honestly. 

I'd be down to play bad vamp, good vamp, hunter, human getting dragged into this, idc. I do have a vampire and human in mind--assuming that you'll allow more than one character--that are kind of a vaguely related set? I have so many vampire lore-based characters...

The religious lore will be fun, too! It's not my go-to but it'll be a nice change of pace! So many RPs just...aren't interested in that aspect of lore.