If you want one to last a long time, get one for a full grown size GSD, a pup can still eat out of it.
We use a water dish that has two bowls attached to each other, so its like two large bowls in one!.. So i fill it up 2-3 times a day for all the dogs, also my dog has a tendency to drag it across the floor when its almost empty, (even if there is a little water, she is quite picky) so if i had anything bigger than this, i think i would need more than a towel to clean it up, otherwise i might have gone with something bigger so i only have to refresh water once a day..
Food dish size, 2 quart i would say is about average size. That would probably work just fine!