Silver Chair and Magician's nephew are a close tie to me. But in any case I'm happy that they're doing magicians nephew...
Horse and his boy would feel really odd because the children aren't really involved at all (except their older selves)
I guess you could say the same thing for the magicians nephew... but HAHB felt like more of a side story (I wish there were more of these)
But I do hope they eventually do the Silver Chair and then the Last Battle