I think in either scenario, the child would not have access to the light and would just be a normal human or awoken child. We as guardians get our access to the light through our ghosts, and a ghost can only have one guardian, so it doesn't seem very plausible for a child of one or two lightbearers to wield the light, unless a ghost chose them. It's a very interesting theory, there might be something in the lore about it already but if not maybe we could eventually get a lore explanation involving guardians and reproduction. To be honest though, I don't think I'd want to get freaky with someone as a guardian, considering my ghost would have to watch