If he can handle the complexity(yes, I know it's more simple and less complex than some other MMOs) I would say let him play. There might be some people talking about mature subjects in chat, but 10 year olds are a lot more street savvy then we give them credit for.
Not only that, if he likes Tolkien, the visuals will blow him away. Like seeing Weathertop for example.
Life is not a journey to the grave with the intention of arriving safely in a well preserved body, but rather to skid in broadside, totally worn out & proclaiming "WOW, what a ride!"
Continuing the never ending battle to keep Lobelia Sackville-Baggins in check