Call me a jerk, whatever. I do not find other people's kids cute. I do not want them touching me, hugging me, offering their nasty goober toys to me. If they wave or say hi, I was give a quick smile and mutter hi back and then look the other way avoiding eye contact with my ear buds in or fiddle on my phone.
Please do not encourage your kids to talk to strangers and carry on all cutesy wootesy. Encourage them to be friendly and then respect boundaries. Encourage them to understand the difference between stranger and friend.
Keep your sticky, germ covered chatterboxes to yourselves in public please. I willingly bore one rugrat. I did not choose to deal with the ones you brought into this world.