Views Argument With Taxonomy: Term Name

I'm using views with an argument for taxonomy term names. It's actually working great, except I cannot figure out how one might show all the child terms in the argument as well. I figure it might be possible through the "option" or "wildcard" text boxes, but I've been unsuccessful. Am I overlooking something? -- And if not, is this possible by using the argument code? I've searched around but I haven't found this specific question, but instead people who want to group terms. If anybody can point me in the right direction, or provide information, It'd be much appreciated. :)

If I have the following:

Animals
--Dogs
----Chihuahua
----Boston Terrier
--Cats
----Lion
----Tiger

If I have a views set up to the url "animals," I'd like the argument "dogs" (http://example.com/animals/dogs) to return all nodes tagged with chihuahua and boston terrier as well. Also, how difficult would it be to limit the arguments to certain vocabularies? That's something that just occurred to me, so I haven't searched for that specific answer yet.