I heard an interview with one of Méliès's descendants on NPR, and she said she thought he'd approve of the 3D technology too. I'm not so sure. In the same interview she mentioned that Méliès was opposed to movies with sound, so he definitely wasn't a proponent of technology for technology's sake. And the film shows how stubborn and recalcitrant he could be.
On the other hand, in the rare cases like this movie when 3D actually lends a sense of magic and whimsey to a film, I'm sure he'd approve. :) It was a fabulous film.