Am I over paranoid? I notice my kids' childcare page have this Bangladesh guy liking photos of the kids. I clicked in to see his profile but notice he is not married & have no kids then why he is in the page? I don't know but I feel very uneasy

I would definitely bring this matter up to your kids' childcare centre. If the group is sharing pictures of your children, I would say it should be private and by invite only. This stops random people from joining the group. I wouldn't worry about it too much until you get more information from the school!