You should just buy your own computer programme. My Mum used to teach me and that was back in the 90's so there must be good fun ones for young ones now. The BBC has quite a good one with different levels.
http://www.bbc.co.uk/schools/typing/
Its just practice, I dont see the point spending money on lessons, they'll pick it up eventually. I also used to play computer games where you had to type what you wanted a character to do, this also helped and was fun.