Well it's almost impossible to have a perfect looking backyard if you have large dogs that run loose all day. You can train your dogs to stay out of certain areas, but ultimately if they are left to their own devices, there's no guarantee they won't get bored and ignore training when you aren't around. The best way to handle this is to only let the dogs in the backyard when you are there to supervise them and to walk them as much as possible to burn off their energy. Dogs need more stimulation that being left in a backyard day after day. And, I would suggest you create an area in the backyard just for them. A kennel will work well and keep the dogs safe. In my case, I have 6 dogs and none of them are left alone without supervision in the yard. When we are not home they are in the house or in a series of kennels we have set up in a weather-protected part of the backyard.