There's a lot of wear and tear involved with pianos just from simply moving them around. Parts of it can get smacked into corners, walls, doors, etc. They're pretty cumbersome so people tend to steer them poorly. You'll want people who have dealt with moving pianos before to make sure they get from point A to B and back safely.

 

I think if you're letting a professional play it it's ok as long as it doesn't take any hits in-transit. If you're going to let just any person walk up and play it then I'd be pretty hesitant.