I used to walk by a school on my way to work and my schedule usually had me passing by at recess, every now and then some kids would recognize me as the "7-11 guy" (where I worked for years a while back) or I'd toss a ball or a frisbee back over the fence for them but I can't imagine someone just stopping unprompted to "watch kids at recess" not looking super creepy even if there was no malicious intent.