Is a shetland sheepdog a good dog for me?

we have been thinking of getting a shetland sheepdog but have heard they can be couch potatoes. we have a large backyard and there are 2 kids, 12 and 14. we want a dog that is energetic but not one that needs a 4 km walk each day, the dog wont be left alone all day either. i have also heard that they can bark non stop, is this true??? and can you reccomend any other good breeds????