Steve

We have a similar problem on a lawn/garden twice the size of yours. Our two puppies arrived in November - along with a load of snow! You can imagine the mess of two quite active pups - chasing each other round the garden. This is not the first time we have had pups - but I have to say these two are the most challenging we have had. Our 10 foot pampas grass has been reduced to a trembling stump! The grass has been trodden and dug up. So we bought them a run and put a small enclosure round it - enough for them to exercise when we are not around to supervise them.
However this does not stop their digging tendancies. They feel obliged to dig where ever they please - they are looking for water to play in. So we are getting not only a paddling pool for them but also we will be using some turf protection mesh for the garden - we will use it in their enclosure and also the part nearest to our house. It is quite expensive but we feel that is better than tethering the little darlings up. They do this even after lots of exercise! I hope they grow out of it soon. Despite all of that we love them to bits.