The official Oz Museum is located in Wamego, Kansas. Not much else is in Wamego, to be honest, but we had a groupon, so off we went one day. It's on the main drag through downtown. Blink and you'll miss it.
I'm ashamed to say my kids aren't as familiar with The Wizard of Oz as I was at their age. But it was also on TV fairly regularly, and our only copy now is VHS, and our only VCR is in the basement. They found the museum interesting enough, but would have liked it better if I had prepped them with the movie beforehand.
That have tons of memorabilia from all the books, not just the one everyone knows. It was quite a cultural phenomenon.
The Wicked Witch gets her army from West Point rejects.
The generation raised on Star Wars prequels was not impressed by the special effects.
They did, however, like the tornado machine.
They had some pretty cool t-shirts. I got a mug that says, "Don't make me break out my flying monkeys!"
The best time to visit is probably during their "Oztoberfest." Unless you don't like crowds. Then any other time is fine. Good for killing a couple hours or stopping on a long trip.
You can do the whole thing in a couple hours, unless you are a die-hard WoO fan. For local eating there are several fast-food joints, but not much else. Topeka is not very far away.