bird-
thats cool you're insulating an old home! i've been slowly doing the same. i recently spoke with 4 different insulation contractors for a larger job of mine. the general consensus is to NOT use cellulose insulation. heard of many problems with mold, fire and settling issues. it is mostly made from shredded paper, not a very good with fire. granted it is treated. it is also way heavier than fiberglass insulation, so the settling problem is worse. fiberglass also fairs better if it ever gets wet.
sure the stuff is made from recycled content, but then it's sprayed with a (i'm guessing) chemical fire retardant. fiberglass is now available in formeldhyde free versions.
everyone says foam, but realistically, foam is 2.5X the cost. if you can afford it sure, great! if it were me, i'd blow in F free fiberglass.
check near your exterior corners with a stud finder, some times in pre 50's homes, they used to run diaginal blocks from the top plate in the corner, to the bottom plate 10 feet away or so. they were trying to gain shear from blocking.
i say go for it with something blow in, and it may not be perfect, but it will be way better!
adam