I'm another one who's been out of school for 5+ years. I'm planning to ask my current boss (she has a Ph.D., but not in Education), a colleague who basically hired me (she has a Master's in Education) and....then the third's kind of up in the air as far as whether I go with a different colleague whose work I've been editing, or another former boss, now colleague of mine. I won't be asking my former professors, though.
Hope that's useful!
By the by, I have a personal statement requirement for one of the schools I"m applying to, so if you have that on top of the SOP too, I'd mention the illness in there, perhaps.