Do you have access to a pool? You could do swimming or even just kicking and it shouldn't exasperate your heel spurs.
I'd say walking (start w/small distances and increase gradually), but I'm not sure how that would affect the heel spurs.
Another thought is if you have a gym you go to, doing some of the leg machines there won't put strain on your heels (i.e., leg extension machine; hamstring curls). Ask for advice - some machines (like leg presses) do use your feet more.
Maybe post this Q in the fitness message board (mention the spurs) and see what answers you get there.
Best of luck and delighted to see you around here!!
I'm giving you a woo-hoo for being you and being here!