The Cinema In The Shoppers' World was dedicated, along with the mall, in October 1951.
Photo from www.generalcinematheatres.com

The Brockelman's Brothers grocery store, another charter mall tenant, was acquired and rebranded by the Stop & Shop chain. The conversion took place in September 1953.
Advert from the Stop & Shop Supermarket Company

The Fountain On The Mall was installed on the Central Green in October 1963. Patterned after water features at the 1939-1940 New York World's Fair, it featured synchronized colored lights and an accompanying musical soundtrack. This played over loudspeakers placed throughout the mall. In this snapshot, we also see the storefront of the J.G. McCrory 5 & 10. It joined the mall in late 1962.
Photo from http://natickmass.info