I don't have a good answer to your question but would make an observation. Musical instruments (from what I have witnessed) are like Gold in Jamaica. They are prized possessions and you will be very lucky if you find someone who will let them out of their control.
In fact, many of my friends simply buy a used "knockaround" guitar to use while in Jamaica and then leave it as a gift. You might want to consider that option.
There are a lot of musicians in Negril so it may be possible to do what you are looking for. Others can speak to that. Good Luck and a great way to make a wedding day more memorable!
Peace and Guidance.
