ordalie:
is it true you can disinherit your own children and choose freely who wil inherit?
Depending on your local laws (which might be quite complex), you probably can't totally disinherit a legal dependent, such as a minor child and perhaps not even an able-bodied wife.
I believe one fairly watertight method to disinherit someone is to mention them by name. Often done by sending "greetings", or "respects" in the text of the will. That way, they can't claim that they were somehow forgotten by the senile old dear.