Hi Celeste,
Is it all the cats spraying or just one? I had a cat that sprayed - a female of all things. I took her to the vet who checked her for a bladder infection. When that was ruled out, we tried prozac. Years and years later, it turned out that it was a bladder infection all that time - the vet didn't get a deep enough sample. Once the bladder infection healed, the cat stopped spraying.
I have used moth balls in my planters to keep the cats out. That may not be a good idea with a two year olf. Is there anyway you can tarp the area when the kids are not using it. (I've seen this done at preschools.)
Best wishes to you.
J.