"No one really knows how to rough it these days. Like you girls, for instance. Probably got cell phones and laptops and space heaters and space coolers and seven different kinds of trail mix. At that point you're not camping, you're just lounging around in a less-enclosed living room. So many creature comforts...but I can fix that!
HYAAH!
Ah, see, there you go! With paws you won't be able to open that trail mix or turn the dial on your space heater. You'll have to get out there and survive the old-fashioned way! Don't worry, as cats, you're nature's perfect predator...just about the easiest form I could've given you, really. You'll be munching on sparrows and destroying fragile ecosystems in a matter of hours.
Hm? Oh, there isn't a set duration for all this. You'll remain as cats until you've properly learned to take care of yourselves out here in mother nature...you're both smart girls, I'm sure you'll figure it out in no time. No need to thank me for this opportunity, enjoy!"