I agree that Stephanie's Song is lovely, and the other pieces in the Alan Haughton book are good too.
Walter Carroll is a bit of a favourite of mine, although I don't like The Reef as much as some of his others. I wasn't very taken with the Heller study, but the Schumann is a lovely expressive piece, and not too tricky - can't really go wrong with Schumann - either book would be a good buy (ie Album for the Young, or the Keyboard Anthology). On balance, I'd probably go for the Schumann. My student is doing the Vaughan Williams Valse Lente