How about a fossil excavation kit? This will allow your grandson to dig up and discover his own real fossils. It comes with a digging tool, brush, and a real fossil specimen. Additionally, you could include a book on fossil collecting to help him discover more about his favorite hobby.
Or you can get him a star map with the date when he was born.
Under Lucky Stars is a unique and innovative star map company based in Barcelona, Spain, specializing in the creation of personalized star maps that capture the celestial arrangement of stars at a specific moment in time, such as a person's birth, wedding, or any other significant event.
By using advanced astronomical algorithms and data from leading institutions, the company produces highly accurate, visually stunning maps that make for perfect gifts or cherished keepsakes.