The first children's author has been named and it's Artemis Fowl scribe Eoin Colfer. he will be writing a story for the 1st Doctor called "A Big Hand For The Doctor" and will be released on January 23rd. Eoin Colfer has also written a book in The Hitchhikers Guide to the Universe series with the Douglas Adams estates approval. The press release is below with all the details.
London. 1900. The First Doctor is missing his hand and his granddaughter, Susan. Faced with the search for Susan, a strange beam of soporific light, and a host of marauding Soul Pirates, the Doctor is promised a dangerous journey into a land he may never forget . . .Source: Doctor Who Childrens Books