What kind of contact has he had with children in the past? If they've done stuff like pulled his tail or something else he didn't like, I could understand his not wanting to be around them.If he usually has no contact at all with kids, he's probably not quite sure what those short two-legged creatures are. Maybe you need to work with a willing child (and parent) to set up an introduction. Make sure you're there since your dog trusts you and he believes you when you say it's all right. Good luck!