Hi - we did just this for our two dogs, but they are inside pets and only use it to potty. I'm not sure if your dogs will be there 24/7... Anyway. We do not use anything for the smell. Somedays it is bad, some days it's not. Most of the time it's not, but I do try to pick up poo several times a week.
We were mainly concerned about the urine smell, and again, on a few hot rainy days it has been a little smelly, but 95% of the time it's fine. The rocks do get hot, but the dogs don't seem to be bothered by it. It's also great because of the small snows we get - the snow melts quicker on the rocks than in the grass, and my two precious pups think they are way to good to go out in the snow ;-)
