I feel that GM'ing anything for my kids makes me a better GM. They tend to throw things out that most adults wouldn't do and then you have to react to that.
Me = Me
G = My then 8 year old son playing Regdar from the WotC 3.5 beginner's box.
Me: Ok, so Regdar comes around the corner and is face to face with a lizard man who stinks really bad.
G: Um... I run away.
Me: Are you sure? I think you can take this guy.
G: Nope. I'm outta here. It's dark and spooky and the stinky-lizard man might hurt me.
Me (after a moment of thought): That's entirely reasonable.
That game needs conflict so it derails without it. Now, with Little Wizards, I've had to think outside the box on more than one occasion.
Me = Me
M = My then 4 year old daughter. (Almost five.)
Me: Your friend's cat ran away. What do you do?
M: Go find it.
M: I'll cast a spell so I can talk to my cat. (Her familiar.) (Rolls and ends up with a complication; decided that she can talk to animals but not people.)
Me: (Now playing two cats, a dog, a bird and very confused people who are hearing her bark, meow and squak.)
M: You're funny daddy.
It was awesome!