Music Composers Unite!
At that tempo, there are a couple of challenges I see; in mm. 38, the independent playing in the marimba is very, very tricky. While maintaining a roll in the right hand, the player, in order to make the leaps, has to swivel his wrist back and forth to reach the wide intervals. I think I saw a couple of such places where, while playable, it would take a great deal of practice even from a pro to pull off with the precision you are probably hearing from the playback on your computer.
In addition, again at this tempo, the switching of instruments would be very tough. You might consider making this for a group of 4-5 players instead of a trio. Would love to hear a recording of this!