I don't think that's strange, and I don't think it's bad: nor do I think it's something you're doing because you're a man. Even in gathering of my closest frie

I don't think that's strange, and I don't think it's bad: nor do I think it's something you're doing because you're a man. Even in gathering of my closest friends, where we share implicit trust that every parent is looking out for all our children, I still take great care to be aware of where I'm placing myself relative to a parent and his or her child. If I find myself blocking some parents' view of his or her child, I move. I (obviously) don't do this because I think they'll suspect me of some malfeasance, but simply because I know they'll feel ever-so-slightly more comfortable being able to see their kid. Playgrounds are the modern analog to a watering hole: an ad hoc "tribe" forms around them, and by making it clear that your kids are at the playground, you're saying, "I'm not an outsider, I'm a member of this tribe, you can feel comfortable with me." Women do exactly the same thing, it just manifests differently; usually in the form of smalltalk and mini-conversations with other parents.