The first scene in “Grown Ups 2” depicts a deer urinating directly onto Adam Sandler’s face. The penultimate scene (spoiler alert) depicts the very same deer apparently castrating Taylor Lautner. These bookends are not only the film’s highlights, they also represent the closest it comes to establishing any sort of narrative throughline. Among the slackest, laziest, least movie-like movies released by a major studio in the last decade, “Grown Ups 2” is perhaps the closest Hollywood has yet come to making “Ow! My Balls!” seem like a plausible future project. It is all but guaranteed a strong opening weekend.