What should I do with these two cats?

These poor cats have never been socialized to litter boxes and treated in a civilized way, so they don't know any 'manners'. Unfortunately, if they are adults, it is going to be very hard to TEACH them any at this stage in their lives. If she left any money with the cats, I would donate them to a no kill shelter (along with the money) where they will be well looked after. Barring that, finding another home where they could be outdoor cats would not be a horrible idea. You could try to train them to litter boxes by confining them to one room, say the bathroom or a laundry room , where you put two cat boxes (with 2 cats you are supposed to have 3 litter boxes, but in one room two will do if you clean them really well) and their food and keep them in there till they are going in the boxes reliably. Then you could try a different room with the boxes for awhile till you trust them in the whole house. You can cover your furniture with throws or plastic to protect it, I don't recommend declawing older cats that pee and poop all over the place because then they can't become outdoor cats if necessary, and declawing is horribly painful for adult cats. Good luck!