Just make sure your next-of-kin knows that that is what you want, because even if you have a donor card or it says on your license you're a donor, if your next-of-kin balks, it can be an obstacle.

Personally, they can have anything they want of me when I'm done with it. My mom needs kidneys and she won't take one from me, so it will have to come from someone else. I'd have to be a pretty big butthead to want someone else's kidneys for her but not be willing to leave mine to the next on the list.