Urine Stain

I second the Nature's Miracle.

Apple cyder vinegar will take the urine smell out of nearly anything. We've used it in the laundry, on furniture like the sofa or a mattress and the carpet. Put it in a spray bottle and wet the area, let dry and then clean the spot with a sponge and your normal fabric cleaner.

Spray the mattress with a solution of vinegar and water, maybe sponge it some. Let it thoroughly dry.

ok so here is an idea and i know it has worked for our towels and clothes. We have a cat who will pee on clothes laying on the floor and there had always been that left over slight smell after washing. When we switched to melaleuca it was all gone our clothes and towels have never smelled so clean. Get some melapower laundry detergent and spray it on the mattress and let it set for a while then blot it up. melapower is 100% natural and so you will be able to have piece of mind to allow your children to lay down on the bed and not worry about skin contact with a chemical.

Vinegar and water works so does Nature's Miracle. I also recommend getting a waterproof mattress pad. I got mine at Penney's, it has plastic on the underside, saved my mattress a couple of times. Just don't put it in the dryer.

Try Nature's Miracle Urine Gone (or similar name) sold at pet stores. We've had a history of peeing cats, and that has taken the smell (and most of the stains) out of everything! You really have to saturate the area though and let it fully dry. I'm guessing it would take at least 24 hours on a mattress, so you might want to use a sleeping bag for a few days till you're sure it's totally dry!