Hello all, hoping someone can help me here!

I'm looking to arrange 'The Dark Island' for my community choir and want to make sure I do this without any boundaries crossed in terms of copyright. The lyrics that I know and would be using are the same as the original post. This could possibly be performed later on to the public, so would like to make sure I'm not standing on any toes before I go ahead and create a nice arrangement.

Any help would be great, thanks everyone