That's a bit of a loaded question, don't you think? Range/tessitura-wise I think you do a pretty good job of using the nice sounds from each instrument.
The key change was relatively smooth for a whole step change.
The ending portion where the two instruments switch off feels a little bit out of character since the instruments blend together so nicely until that point. Maybe have them end homophonically (melody/accompaniment) or even polyphonically (two different melodies) to bring back that unity just for the end.
It could have gone more places dynamically, especially text adventure games like that can get a little too in your face, but this variated enough to where the track as it now can be laid down. I'd experiment if you have some time though.
I think it sounds great! You have a lucky friend.