I want to show the program of my young cousin (12). I think LOGO is a good start. Which implementation should I use? (Window)
I would use this for windows
I would not teach Visual Basic to a person or child who starts programming, rather than the static language that he prefers. Also I will not teach PHP to anyone, but this is a personal taste.
You can also take a look at Alice. What language is used by some people to teach children.
http://www.alice.org/
You might also want to consider Small Basic: http://msdn.microsoft.com/en-us/beginner/ff384126.aspx
I have no experience with this, so I can be a little off the base, but it seems to have a few fans:
Starlogo TNG is a good graphic implementation of the logo that can make it really interesting for children. It uses a block-programming interface and three-dimensional graphics, so it looks at the children as if they were playing a game right away. http://education.mit.edu/drupal/starlogo-tng
Something else that I used earlier is RAPTOR, which is a block diagram interpreter. This is good for teaching algorithms at a high level without the need to simulate training time. http://raptor.martincarlisle.com/