This book, "Hello World: Computer Programming for kids and adults" http://www.manning.com/sande/ might be a good place to start once your child is older. It's written by a father and son and documents his son's foray into programming using Python. I believe his son was 10 at the time.

Personally, my parents got me an Intellivision at the age of 6 and I played it every day. By around 4th grade, I wanted to start writing my own games so they got me a Commodore 64 and a couple of books with game listings in Basic and I started having more fun writing games than playing them.