As most of you have experienced, in Fallout 3, you could not kill children.

However, the developers of New Vegas have said that you will be able to kill all but one person in the game.

My questions are:
Will there be any children in this game?
Will we be able to kill children, if there are any?
Will that one invincible person be the only kid in the game?
Or did the developers say this without taking children in the game into account?

There is more than one child, and no, you can't kill them. The devs ignored children for that statement.

1) Probably, but not as much as in Fallout 3.
2) No and discussing such a topic will result in this thread being locked
3) Perhaps
4) And perhaps once again.

There are children. The Child at Heart perk is about. You can't killed them. Further mentions of killing all but one character in the game have had been amended to say excluding children).

I wonder who you can't kill

i was wondering the same thing.
either
1. there are no children
2. you can own children
3. they didnt count children when they said that

i knew it was 3 though, but its always nice to get confirmation.

Discussion of child killing is a restricted topic on these forums.