Okay. My cousin remembers this movie about 2 kids who go on an adventure and walk on a sideways sidewalk. Any ideas?

The closest thind to the steps idea I remember is" labrynth"

Except in the Labyrinth, there wasn't 2 kids going together.
The part with the stairs was Sarah trying to go after her step-brother, Toby.
I think it's a different movie, but which one I'm not sure of yet.

Whenever you hear about a "sideways sidewalk", the answer can only ever be... The Hugga Bunch Movie (http://www.imdb.com/title/tt0173915/). In France, there are rumors that those who have seen it have been cured of gout and bursitis. It's just that good.

Yep I agree,
Its definatley the hugga bunch.
I still have this movie.