Yes, this. Listen to what the dude is telling you. When he says he knows how men look at them, he's saying HE saw them as sexy. And if he thinks that's an appropriate way to signal that to you, he's probing you - maybe unconsciously, but he's trying to see how much he can get away with at some level. If, on the other hand, he actually had their best interests in mind, he'd say something like, "Oh, hey, I saw your kid the other day - do you think she'd mind if I said quick hello when I saw her? She looked like she was having a great time, so I didn't want to intrude with grownup stuff."

Of course, if he has to even have that conversation with dad, that's telling me something. I know a number of kids, ranging in age from under 10 to, well, they grew up and ain't kids anymore. I know them, and I know their parents, and if I happened to see one of them around town, I'd already have enough of a relationship with them to know whether saying hi would be welcome. And more to the point, they would have an idea of what I was about, and have a number of resources to call on if they thought I was sketchy.