Ask HN: First programming language for teaching programming to children?

I have a two-year-old daughter and I've decided to teach her programming when she gets older. The two languages I've considered are Scheme, for its simplicity and functional focus, and Smalltalk, for its solid grounding in OO. Have any of you taught programming to children, and what language did you use? And incidentally, how old was the child when you started teaching?