We're definitely in THE HILLS HAVE EYES territory here. It begins 14 years ago with a woman giving birth to a mutant. We don't see what the child looks like, though the priest that shows up is about to shoot it. The father prevents this by killing him. In present day, an American family is visiting Ireland and they encounter this group of bloodthirsty mutant children. Most of them wear sacks over their heads, though there's one particularly creepy girl that has these lidless eyes. Basically, it's a gritty VILLAGE OF THE DAMNED.
I've seen so many horror movies like this that I can't really recommend it (they all blur together) but there is an amazing scene in which a guy's head is cut in half, through the eyes, with piano wire, that made me cringe.