Like Monrein, I received a kidney from my sister-in-law (husband's sister) on Nov. 5th. My thoughts on living donors has always been as long as they are fully aware of what they are doing, that they are doing if for the right reasons, they understand the potential risks of surgery and recovery, and that they know how they must take care of their remaining kidney, I say GO FOR IT! They are offering because they love you and they care about you. That takes a special kind of person. Don't poo-poo their generous and selfless offer. THEY LOVE YOU! Just be sure they have all the information.
Good luck with whatever you decide. It's ultimately up to you, of course.