The summer’s sequels are opening big and dropping fast…and here come two more. Warner Bros. and Village Roadshow are opening “Ocean’s Thirteen,” and Lionsgate has high hopes for “Hostel Part II.” Both will be competing against the pesky “Pirates of the Caribbean: At World’s End” and Universal comedy “Knocked Up,” which grossed almost $30 million last week and has great word of mouth. Tracking indicates that the third installment of “Ocean’s” should see the biggest opening in the series. Original film hit $38.1 million back in 2001, while the follow-up moved the mark to $39.1 million. “Thirteen” is opening in 3,565 theaters. Meanwhile, “Hostel Part II” is slicing its way to 2,350 theaters. First film chopped off $19.5 million in its opening weekend last year. For families, as “Shrek 3” plays out, Sony enters the marketplace with its PG-rated animated entry “Surf’s Up.” Film, about a surfing penguin, slides into 3,528 locations.