Julia, since you are a little concerned about the demands this position might make and your health concerns, why don't you ask for a co-chair to work with you. I'd just explain my concerns about health, etc and emphasis that you'd be glad to be an organizer but will definitely need some help from someone that has the history that you will need, too. Good luck--you sound like a good program chair--or any office! Wish you were in my guild!