"2010: The Year We Make Contact" is a much more accessible movie that holds up pretty well. It also feels like a payoff after investing so much time being confused/bored by 2001.

I was 11 when "Logan's Run" came out. Yes it's kinda loaded with 70's sex tropes for the first act, but it's also equal parts goofy and a really good film.

The original "The Day The Earth Stood Still" holds up.

"A Boy and His Dog" is a bit crude here and there, but might resonate with a 12yo.

"Quatermass and the Pit" (aka "Five Million Years to Earth") is both intense and fairly tame.

A lot of old TV series hold up - Twilight Zone, Outer Limits, UFO, Space 1999, Star Trek TOS, etc all have some excellent episodes.

I absolutely love "Dark City" and "12 Monkeys" but I'm not sure they'd have held my interest at 12.

Doctor Who, both old and new are excellent. Though I'm partial to the Tom Baker era.

The Stargate franchise is pretty good.

"Moon" (2009) is a bit cerebral but a good SF story.