You shouldn't need to change directory names in order to use a "filename (path) contains" statement. You might need to surround your search term with double quotes like "childrens movies" .
But really, directory organization, while a good thing, is a terrible way to categorize your movies. Why not simply do a search on your master movies view for "children" and then tag all of the movies with a Genre of children or similar? Then you can build a view based on Genre and be done with it. Or, if Genre doesn't work for you, use Keywords. The point is, that directory paths are rather limiting and MC isn't designed to use paths as a primary organizational method.
Good luck.
Brian.