Thumbs will have no effect. If it matches your wishlist, Tivo will record it. However, what you can do is add some "not" keywords in your wishlist. For example, add the keyword "Futurama". Then, in the list of keywords, highlight it and then hit the down thumb button until it has a "-" before it. This will now update your wishlist to exclude any programs that contain the word "Futurama".
You can try adding a (not) "Animated" keyword, but I'm not sure if the categories are in the relevant keyword fields or not. Worst case scenario, you could add a (not) keyword for each kids' show title you notice it recording. It could be a little tedious to set up at first, but each time you add a show you don't have to worry about it ever recording again.