Sorry, late post on this thread, but I would really recommend the southdown for your circumstance.
They have a slow metabolism, which you will need as two ewes with a potential of 4 lambs in the spring, will soon get through 1/2 an acre and you will want to avoid buying solid feed or hay to feed them up on (expensive). You'll get a good carcass by autumn from April lambing. They are easy to lamb, docile to handle and smaller than other breeds to turn over. The meat is superior to many others, often favoured by top quality restaurants, for its sweet flavour.
Only slight downside is they can have bad feet, make sure you get some with black hooves and ensure they are solid at purchase. I have heard they are bad mothers, but never had any problems with mine.