If you put a litter box in their cage--I used one made for ferrets, and ferret litter--they'll use it to pee in. If they're outside the cage, they'll go back in to pee. Or you could put another litter box in their play area. Just don't use any old litter; the kind made for cats is too coarse for them.
They aren't as fastidious about their poop. Sometimes they'll poop in the litter box, and sometimes not. But they poop hard little balls that are easy enough to vacuum up.
You could, of course, always try to teach them. They're very open to learning things, and quite smart and affectionate. Just keep an eye on them when they're out; they chew things. Early on, I had one who could snip through a modem cord like a pair of scissors. I got a lot of practice with wire stripping and reattaching.
