Robert Rodriguez has a soft spot for cheesy special effects. Spy Kids 2 was a tribute to Ray Harryhausen, and this latest installment honors another B-movie classic, 3-D. This means that for most of the movie you have to wear uncomfortable cardboard glasses with different-colored lenses that will probably leave anyone over the age of 12 feeling cross-eyed. They come in handy, though, when Juni Cortez (Daryl Sabara), the youngest member of the family of super-spies headed by dad Gregorio (Antonio Banderas) and mom Ingrid (Carla Gugino), enters a video game to save his sister Carmen (Alexa Vega), who’s been trapped there by the latest Spy Kids villain, the Toymaker (Sylvester Stallone). The 3-D looks cool, but the story in this installment, unlike those in the first two films, remains two-dimensional. And though Ricardo Montalban returns as the kids’ grandfather, other than donning some superhero duds he doesn’t have much to do. Like its predecessors, Spy Kids 3-D emphasizes the importance of family and friends, and the possibility of redemption, but by the time Rodriguez, who also wrote, edited, and scored the film, gets around to moralizing, it’s hard to care — you’re too busy squinting at the screen and trying to refocus.