Song's good, I quite enjoyed it. It came across as pretty professional!
Too bad for the title though. The preposition "cum" comes in default with an ablative. This means you would have to say 'umbris' if you meant 'shadows' and 'umbra' if you meant shadow. Also, the plural nominative of 'amicus', is 'amici'. The version you used is the accusative. Which would be weird, because we're supposed to be friends with shadows, which would make it the predicative nominal, and therefore it would get the first case. Amici cum umbris.