What toys can I give to my autistic grandson?

Limited choices. Unfortunately, there are few toys developed specifically for autistics (but I am aware of one great idea that is in development). You have to use toys/tools/devices designed for the "regular" population. Just competence or even mastery with a toy is not enough. The goal should be to encourage interaction with others & to feel/express emotionally.
Ones that require. Him to interact with his family; anything that promotes turn-taking, social interaction & social communication. See carol gray's social stories books, published by future horizons. Some items teach facial expressions. There are "timed-timers" visual cues to prepare him for transitions. Amazon has wooden melissa & doug toys for pretend play & wall calenders for him to see daily schedules by m & d.