Grady is a fabulous, underused name that fits with the colonial cool of names like Silas that are just starting to hit the charts, and Nathaniel, which is firmly established as a current favorite. Marcus Joshua is great, too.
Mallerie and Vallerie both look a little odd. (I'd prefer Mallory and Valerie.) And Natalie is okay. So I'm ranking your mouthful of a given name - Margaret Anastasia-Elizabeth, with the darling nickname Mae - as my first choice. Any chance you'd opt for something a tiny bit briefer in the middle, though? Margaret Ana-Elizabeth, perhaps or even Margaret Anne-Elle?
Just a thought. It is a regal name.