I take it you haven’t heard from Vivendi yet 
I don’t know what names you want to use in your book, but I know that there is a publisher named Oberon and afaik they haven’t been sued yet…
Also, the names Oberon and Titania have been used in Disney cartoons and other stories. Disney doesn’t own the rights to the names so I think you’ll be fine.
If you get in trouble, you could always pull a “Dan Brown”! He copied and used so much material from other resources (like Holy Blood, Holy Grail) and he still won the lawsuit.
All kidding aside, if you really want to write the book and are really commited to finishing your project, you might want to contact a publisher or lawyer. All we can do here is speculate.
We don’t want to get you into trouble you know!