I just adopted two kittens. They are both 12 weeks old. My problem is that my cats both like to play and roll around in their litter box. They make a mess which isn't too big of a deal. The idea of cuddling with my cats after they were just rolling around in their own mess isn't very atractive. Any ideas on how to solve the play issue?

Time, sadly. Anything that makes them not want to play in the litter unfortunately may make them not want to USE it. They will grow out of it.