I think it is an excellent idea. In this economy, with many rescues having to turn away dogs due to lack of space, I wouldn't want to count on a rescue group to take my dogs.
I have had extensive conversations with friends and family members and where my dogs go has already been determined. Just as I know which of my mother's pets I will need to make room for should something happen to her.
I think that everyone who has a pet (or two or ten) should talk to those around them and decide who you trust to take care of your pets should something happen to you. This needs to be done in a very honest and understanding way. I have had, in the past, 2 very lovely dogs with some very serious issues. While I was able to manage them, my family knew that if anything should happen to me, those dogs were to go to the vet and be put down. Both were dogs that had the potential to be very dangerous if mishandled and there was nobody in my life I trusted to that extent.