It sounds like irresponsible people, not really an issue with kids. 7 year old children still need signficant guidance by their elders.

For the urine/poo, the only stuff I swear by is OdorXit. I have tried other products (though not lately), and found them to be lacking. OdorXit IS available readily online, and through some selective retail outlets. It is expensive. 16 ounce concentrate is about $45. I think it is a one ounce to 3/4 gallon.

I use this example: for months and months, I kept some clothes under my bed in those plastic storage containers. One of my kitties (I suspect Minnie) used it regularly for a litterbox. The clothes were nasty, nasty...but, I wanted to salvage them. And, I did. You cannot smell anything on these clothes (or I would have gotten rid of them, just in case anyone was wondering).

I had feral cats live in my garage for 6 weeks. They didn't use litter pans. I will clean the crates/garage floor with OdorXit, and know I will be satisfied. I just don't have faith in other products.

For the crayon stuff....you will most likely need to use a kilz product. But, that isn't my area of expertise....lol. Cat pee is.