After watching the movie "Finding Neverland" last summer and my renewed love for "Mary Poppins" thanks to "Saving Mr. Banks, I have been working on a story where these two iconic characters meet and have an adventure together.  I need to be absolutely positively assured that "Peter Pan" the book is indeed in public domain.   I have an obstacle regarding Mary Poppins and it is the P.L. Travers Estate.  Any help in this matter would be greatly appreciated.