Seeking advices for running a D&D 5e game with middle schoolers

Hi everyone! I’m looking for advice for running a D&D 5e game with middle schoolers (around 13 years old).

I work as a school monitor in a middle school, and for overtime work I run a tabletop RPG club there. I’m about to DM a Dungeons & Dragons 5e campaign for a group of five 8 graders who specifically asked to try D&D.

They’re surprisingly enthusiastic about complex rules and aren’t afraid of the system’s density, so I don’t really need to simplify 5e for them. That said, I have two main concerns.

- First, We only have one hour per week, every Tuesday from 12:30 to 1:30 PM.
My goal is to keep them engaged throughout a full scenario without them losing patience, while still giving them plenty of opportunities to play, roleplay, and develop their imagination (which is the whole point of the club).

I’ve already thought about starting them at level 2 or 3.

Do you have any tips, structures, or adventure formats that work well for such short sessions in D&D 5e?
How do you keep momentum and meaningful RP when time is that limited?

- Second, The kids are completely obsessed with Stranger Things.
Every Tuesday they bring up Vecna, the Mind Flayer, the Demogorgon… (and honestly, even if the show is wiiiiidely open to criticism, it introduced a whole new generation to tabletop RPGs, and that is priceless.)

I was wondering if it could be a good idea to introduce the concept of these overwhelming, godlike threats early on, while making it clear that they’re really far beyond the party’s current power level. (idk, maybe ancient scrolls that mentions the Hand of Vecna, forbidden lore, cult rumors, ancient prophecies, seeing the aftermath of these entities, and so on)

Do you have any D&D 5e settings, official material, or homebrew ideas that could support this kind of long-term, cosmic threat?

And for context: I’m a fairly experienced player, but a very new Dungeon Master. I see this as a great opportunity to improve my DMing while doing something meaningful with (and for) the students.

As for now, I already introduced them the basics, such as Races and Classes, and how to roleplay. Next Tuesday it’s going to be Character Creation.

Thanks a lot for reading — I’d love to hear your advice!