To try to reach more parents, a coalition called Play for Tomorrow this fall staged what amounted to a giant play date in Central Park. The event, known as the Ultimate Block Party, featured games like I Spy, mounds of Play-Doh, sidewalk chalk, building blocks, puzzles and more. The National Science Foundation was closely involved, advising organizers — and emphasizing to parents — the science and the educational value behind each of the carefully chosen activities. Organizers were hoping to attract 10,000 people to the event. They got more than 50,000. “We were overwhelmed,” said Roberta Golinkoff, a developmental psychologist at the University of Delaware and a founder of the event along with Dr. Hirsh-Pasek. They are now working with other cities — Toronto, Atlanta, Baltimore and Houston, among them — to stage similar events, along with making the Central Park gathering an annual one.