What's a good alternative term for "live action"?
You don't need another term. Live Action is the accepted term for differentiation between, well, live action film and other kinds of movies, such as animation/3D films. It's also used consistently for this purpose, e.g. the Oscars use it in their category names:


  Short Film (Animated)
  Short Film (Live Action)


Conversely, I have never seen this term used to indicate a live stream, so nobody will get confused.

There are other terms for feature-length such as feature film or motion picture, however those are rather used to differentiate between feature lenght movies and short films and can also be used for animated films.

If you have a feature-length film, you could amalgamate the terms to something like live action feature film or live action motion picture, but I really wouldn't recommend that.