The “Grown Ups 2” gang partied like rock stars Friday to celebrate the end of filming. The cast and crew of the Adam Sandler comedy gathered on the film’s set in Swampscott, noshing on a serious spread of treats both savory and sweet. Haverhill-based Cakes by Erin handled the desserts, making 350 cupcakes and an enormous confection depicting the Tyngsboro quarry, where a pivotal scene in the movie was shot. (Miniatures of the characters played by Sandler, David Spade, Chris Rock, and Kevin James adorned the cake.) “Adam Sandler was so gracious and nice,” said Kelly Mackin, who co-owns Cakes by Erin with her sister Erin Erler. “We didn’t have to ask. Adam just said, ‘We should take photos with the cake.’ ”