In OW, it mentions that WCVs have "standard vampire weaknesses", but affect them less than others. I don't remember them having any problems with sunlight, holy water, etc, from the books.
"Standard Vampire Weakness" the first: A stake to the heart will easily kill a WCVampire.
And I think they're specifically meaning holy items like the swords of the cross and such. I, personally, would associate it with feeding. The more they rely on their Hunger, the more they can be affected by holy ground, religious symbols, and the like. We've seen Thomas and his sisters move around in the daylight, deal with running water, and Thomas seems to be okay (if uncomfortable) on holy ground.
Then again, I don't remember them ever using any of their vampire powers in any of those cases, either. Maybe it works like a Block (of varying difficulty) on their checks when tapping the Hunger?