Unlike the Boston Children's Museum over in Fort Point, the Museum of Science offers parkinga not-insignificant bonus to the many family-friendly charms of this 230,000-square-foot institution. For preschoolers, there's the Discovery Center, full of stuffed animals, things to crawl on and fidget with, knobs to turn, and levers to tug. For older kids, there are exhibits about dinosaurs, lasers, and other gee-whiz subjects. And for parents? The profound joy of nobody whining about being bored.