10-20 hours for Middle School students

I teach a semester course for 7th and 8th graders. I introduce a variety of computer and media skills, so I can only use Code.org once a week. That means 10-20 hours max. Is it worth starting CS Discoveries? If so, or if not, what path would you suggest? They have just a little experience (with Scratch), and I would like for them to go deeper now.

Note: I have 2 or 3 students who already know how to code (one has done professional level work). Is there a way to start those advanced coders on a higher level course than the other, and what options would you suggest)?