Translation:This is something important for all of you.
I don't really understand the "todos ustedes" portion of this sentence. I would have said "para todos" or "para ustedes", but definitely not both.
it translates almost word for word: para todos = for all para ustedes = for you (plural) para todos ustedes = for all of you
why para todos ustedes? Isnt ustedes undrerstood as meaning "you all"? Why the need for the Todos?
It is putting emphasis on all of the listeners rather than just some. Consider you're in a classroom where you are separated into groups. If you are addressing all of the members of your subgroup, you would use Ustedes, but if you then want to address everybody, you might say:
"¡Oye, escucha! Esto es algo importante para todos ustedes. -- Hey, listen up! This is something important for all of you (where you put extra stress on the bolded words).
"Ustedes" is just "you-plural". There is no difference between singular and plural "you" in English, that is why, to make it easier to understand, "ustedes" is often translated as "you all", while actually it has no emphasis of "all" included.