[apecat]

There's a lot of great picks here, such as Gattaca, Man from Earth, Contact, The Matrix, Wall-E, Children of Men, The Fifth Element, 12 Monkeys. I would add Truman Show.

Depending on the individual and their patience, Primer (2004) might also be a great fit. The pace is a bid subdued but thematically, it's mind bending. I don't think it includes anything particularly awkward as an early scifi movie to watch together with your own child. I would probably start with one of the spectacles from the above picks, though.