I knew someone years ago that had 2 alsatians and kept them in a converted garden shed with a dog run attached. Great idea for protecting the garden but I thought it was a bit cruel for 2 dog to be penned in so much.
My parents back garden is hedge on one side and fence at the back and the other side. Our last dog was rescuded from kennels so wasn't too bad for getting through gaps but the current one was bought as a pup so we used plasticised chicken wire, real chicken wire, spare bits of wood and a lot of blood, sweat and tears to fill in all the gaps. He never did manage to escape so we must have done something right.
On the flip side, having doggie poo and wee un's maybe isn't the best combination so fencing off part of the garden could be an idea if you can afford the space.