I think they were rather cute, mainly due to the dialog. "Come on Mr. Bubbles!" and "I know he'll be an angel soon." They were just little kids, horrific, mutated, soul stealing kids, but kids none-the-less. I never found the creepy, really nothing in Bioshock was creepy with the possible exception of Cohen, but the little sisters and the big daddys were the least creepy. Still, the big daddy's and little sisters were just cute. They were just going about doing their thing, minding their own business.