I agree he screwed up, but I think calling him a danger and wanting to get him away from the daughter is a tad bit overkill especially since he seems to feel guilty and ashamed of his actions. It sounds like to me his curiosity got the better of him and he couldn't control his impulses. He's certainly in the wrong, but his actions doesn't automatically make him dangerous or a threat to the daughter and granddaughter.

I'm not justifying his actions by any means, I'm simply trying to say that there is always more than one side to a story.

If he's truly sorry, I would say allow him the chance to get help and redeem himself, but at the same time, isolate yourself from him until he does for the sake of your own mental health.