Carol,
You have to decide on this one!  It is your health and well-being that you 
have to think about. I am sure you would love to play for the couple and 
fulfill their wishes but you health is more important.  I would not punish 
myself to play when there are several others who can do it and who are much 
healthier.  Do undo all you have worked so hard to do. I am praing with you 
and trusting the Lord to lead you to the correct decision.

Ned