[Rusty]

There are some things I would change. The first is the title of the poem. I believe you meant 'December-the best time of the year'.
If so, add the article 'la' prior to 'mejor'.

Instead of 'elfos', used in the LOTR movies, I would use 'duendes'.

Instead of 'villancicos cantando', use 'villancicos cantados' or 'villancicos cantándose'. You could also just reverse what you wrote.

I'm not sure what you meant by 'Santas mágicas'. Please provide that part in English.

I'm also not sure what you were trying to say about your brother.