I take mine, he's six now but he was going when he was five. I tend to stand him up on the back of the chairs infront when others are standing
Naughty words eh, well it's one of them things isn't it, cant protect them forever and as long as they know there wrong and not to use them...
As for concentration, well from my experience he does tend to ask questions not necessarily related to the game he's watching but that's just young kids for you, in the main he's pretty focussed on the game.
And yeah he's fine in an adult seat