Kids of all ages will be invited to Boston’s biggest birthday party in 2013 as the Boston Children’s Museum turns 100. When it opened in Jamaica Plain in 1913, the museum featured displays of stuffed birds and mammals and shelves of shells and minerals. Today the country’s second-oldest children’s museum is much more hands-on, unleashing the power of play to educate and entertain. To celebrate its centennial, the museum is planning a series of special events. In early April it is cosponsoring an early childhood summit and a parent fair. From April through October it will host biweekly public programs leading up to a three-day celebration Oct. 4-6 that will include a gala dinner, an all-ages dance party, and a festival filled with musical performances, outdoor kids’ activities, and Boston’s largest birthday cake. Plus, the museum will open pop-up locations in parks and neighborhoods throughout Boston in 20