You didn't mention the distance, but 1/2" will work for a WM. If the distance is long, it takes a little longer to fill the machine.
You really want to have a shutoff at the machine. It should always be OFF when the machine is not in use.
You also want to make provisions to drain those lines for the winter. You could have them slightly sloped back to the house, and have a drain cock installed with the inside stop valve.