So now that you have a giant kitty box that your kids are playing in, what do you do? Ignoring the problem isn't a solution, child protective services and all that. Well, you could have a kitty barbecue. That would cut down on future contamination, and would be super tasty. But, it would do nothing for the poop currently in the play area. You could just get rid of your kids. But, the wife has put the kaibash on that. So, if you are a creative, think outside of the box type, here is what you do.
Build a frame, next to the play area. Move the sand and the poop mixture into the new box. Lay some paving bricks over the sandy poop mixture. Something in a nice non-crappy design, like a lovely herringbone. Before you know it. Cat poop? What cat poop? Anyone for a barbecue? Oh, you'll get used to the smell.