It may not be totally true that geniuses are born and cannot be made. I remember seeing the series "My Brilliant Brain" on National Geographic. It talked about how kids can be trained to become geniuses. This was thought possible (according to the program on NatGeo) by providing a nurturing environment so that the child can realize his/her full potential.

You can for example encourage the child to learn some skill at an early age that stimulates the child's brain. There is the example of Susan Polgar (the first female chess grandmaster) whose psychologist father believed that genius was not born but rather made. His way of making genius was to teach the 5-year-old Polgar chess. I guess there is no harm in trying. Teach your child a mentally stimulating new skill (such as chess) or let them learn a musical instrument. Am sure - no harm would come of it.