Plus you can kick their asses if you don't tell them about the game's secrets. I used to play Mario Kart with my young niece and nephew on my brother's old SNES. They loved it but they had no idea about the power-sliding so I could beat them at will. They also never grasped that when you're leading the race the players behind you get better pickups.

I'm not a monster - I would sometimes let them win when the crying got too annoying.