Nick, you take the passage too literally. Immanuel and Maher-Shalal-Hash-Baz are the SAME prophesied child. Immanuel is not a proper name, it is a reference, a nickname for the child, if you will.

It is because of this, that many biased Christian scholars have begun to claim that Isaiah 7 & 8 have a dual meaning, in that they are both a prophecy for Isaiah's wife and for Mary and Jesus. Which is a totally bogus nuance.

Furthermore, the first two chapters of Matthew that addd the virgin birth story, are much later additions to the original book. IOW, these passages are forgeries. Some Bibles even omit these first two chapters because their authorship was added much later.

But I'm sure that was God's intention all along ... or was it?