No one in elementary school (or any of your kids) has ever heard of Animaniacs unless their parents liked them and makes them watch on Hulu. The show stopped production of new episodes in 1998. Why are you looking for that one in particular?
You're better off playing the Spongebob theme (which is again pushing it, but it's at least still on the air), or maybe something like the Backyardigans theme. Even a Sesame Street song would work.