Babies below the age of 18 months, you can't really like or dislike them because they haven't developed a real personality yet; they're essentially a chore.
2-10 years old can go either way, they can either be really adorable or really irritating; a lot of the kids I see around are total brats, but that's because their parents are thick so I can't blame them. Although I think it's really a case of you don't take any notice of the good children, same as anyone else in public, and then the children that are screaming and kicking up a fuss draw your immediate attention so it seems like every child in the world is a nightmare. The children in my family are wonderful and I love spending time with them, but unfortunately I rarely get to see them.
After the age of 10 it's just the same category as teens, adults, everyone, not a fan of most of them, but still plenty of great people.