Basically, they can play around with the app, to get a feel for it in a advance. The target audience is business owners who may or may not (likely not) be technologically inclined.
Demo implies that they might just be watching something (a demonstration).
Interactive Demo feels like it might be a bit too techie for the crowd.
Test can imply that the app is in beta and we're asking them to test it.
Test Drive sounds a little too informal and I don't much like it, but so far seems to be the least problematic choice.
What are your thoughts on the matter?