The kid in the candy shop is Eli Roth with a gore budget and in the “Hostel” director’s latest bloody romp, “Ice Cream Man,” there’s a decidedly childlike giddiness from behind the camera to accompany the sicko suburban carnage depicted onscreen. Little things like style, narrative command and character still matter, and Roth, who wrote “Ice Cream Man” with Noah Belson and even gives himself a role, is decidedly more of a smart-ass vaudevillian than a skilled filmmaker. With its sunny elevator-music-scored opening of cheery park scenes and leafy residential neighborhoods, “Ice Cream Man” sets itself up, not unappealingly, like a Norman Rockwell painting asking to be vandalized. Next comes the arrival of a tinkling blue ice cream truck manned by an eerily silent, smiling, wraith-like purveyor (Ari Millen) with a John Waters mustache. Then the ice cream man returns to refuel his targeted customers, who try to convert our well-cast, engaging trio of young double-scoop holdouts.