Who redubbed Christopher Robin's voice in this film?

Does anyone know who it was who redubbed his voice? I also noticed that it credits the other people who voiced Christopher Robin, even though their voices are only heard in some of the songs.

Finally, how come they didn't redub Roo's voice? He was voiced by Clint Howard in the first two shorts, and by Dori Whitaker in the third one, and both their voices are still heard in this film.