For a kid's playroom - you don't want a plasma.
Inevitably, there will be video games played, and they will leave something on - perhaps for a long time. This is not what you want to worry about with a plasma.
I hate LG as a company due to personally knowing people who have seen their LG displays fail (about half a dozen of them), so I don't recommend them at all.
They have a great price, and their poor build quality is the reason for their great price.
I would get Vizio over LG, and Samsung or Sony or Sharp over Vizio. But, you have to watch your budget I'm sure. Still, you are now informed, so if you go LG, it is a gamble you know you are taking.